Ramjet 502 re-assembly

[chevynut]

I bought my BBC 502 several years ago from a guy who apparently abandoned his project, so I got a screaming deal on it. It was a new, never run, deluxe GMPP ZZ502 crate engine kit he bought without the intake and carb or distributor. When I got it, an aftermarket single plane intake had been installed as well as a cheapie HEI. I sold the intake and distributor and started collecting parts to make it a Ramjet 502 which is the fuel-injected version.

The GMPP Ramjet 502 crate engine has the same internal parts as the ZZ502....forged steel crank and rods, forged JE pistons, aluminum heads with 2.25" intakes, and a steel hydraulic roller cam. The only difference is the Ramjet is EFI and the ZZ502 is carbed. I won't ever have another carbed car engine, so I found a brand new set of Ramjet manifolds for sale locally and bought them, and collected all the correct sensors and other pieces from various sources. I bought the fuel rail, regulator, GM computer-controlled distributor and other parts from GM Parts direct and a new Holley dual 58mm throttle body (stock is dual 48mm), 42 lb/hr injectors, and Commander 950 Pro EFI controller. I am using an MSD coil, stock GM plug wires and stock AC Delco plugs. The final upgrade was a Holley wide-band O2 sensor kit that interfaces to the C950.

The engine was shipped to me pretty sloppily and the oilpan and valve covers sustained some minor damage so I'll need to address that. The exhaust ports were left uncovered and no spark plugs were installed. I put the engine in my frame as I was building it and tried to cover the ports, etc. After years of sitting I decided to tear it down for a cleanup and replace the low-tension oil rings that GM put in these engines that sometimes cause oil consumption issues. There was actually quite a bit of trash in the engine so I'm glad I made the decision to tear it down.

The past week I completely disassembled the engine and took the block to a local shop for a torque plate honing as recommended to my by Total Seal. All the parts I took out looked really good and are laid out on my assembly table. I took the pistons I removed, as well as another brand new set of OEM 502 pistons that I bought when I planned to build my own 502 just in case they needed one or two for a better fit.

When I get the block back I will document the assembly process here. The shop will be removing the cam bearings and all oil galley plugs. Then they will install the new cam bearings and plugs after honing and cleaning the block. I will be installing the crank with the same bearings it came with, a new rear main seal, the same rods and bearings, and the same pistons with a new Total Seal ring set containing standard tension oil rings. I'll order the rings when I'm sure they successfuly honed the block and the pistons fit. ;)

I haven't decided whether to upgrade the cam to something a little bigger or not. I like the sound of the stock cam, but there's a lot of hidden power in the engine that a cam upgrade can release. The valve train can handle quite a bit bigger cam. I will be using the stock GMPP timing gears and chain that I removed. All new seals and gaskets will be used.

On the top end I won't be doing anything to the heads except using new head gaskets (same as OEM) and will probably install a set of roller-tipped rockers with the stock pushrods. I'd like to do full rollers but I want to use the stock valve covers and they won't fit. I like the stock covers and don't want to change them. I will have to machine the upper intake manifold to accept the larger dual 58mm throttle body, since GM thought it would be nice to just make two 48mm holes in it.

I haven't built an engine for several years except rebuilding the top end of my ATV, so I'm looking forward to doing some actual wrenching on this engine.

I posted these on my Nomad chassis assembly thread but decided to post them here too. These are a few pics of the teardown.

http://www.trifivechevys.com/attachment.php?attachmentid=5805&stc=1

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[chevynut]

I still don't have my block back from the machine shop so in the meantime I thought I'd address something that I'll need to do to close the engine up. I probably wouldn't do this today, with the experience I've gained doing the C4 conversions, but early in my project I set my 502 in the frame and was concerned about the height of the top of the Ramjet manifold. I thought there might be interference with my hood and wanted to be sure to address that. I mocked up the hood position as close as I could get it and the clearance was pretty tight.

So in an effort to lower the engine as much as possible, I cut the front of my oilpan so it could be lowered over the rack. I built my engine mounts, and did the rest of the construction of the car. When the car was all mocked up with the front end sheetmetal, I ended up with around 13/16" clearance from manifold to hood which is more than I needed. But now I had my oilpan cut and engine positioned. Lowering the engine like this caused other issues that I could have avoided, but it was too late to re-do everything way back when. The rack is going to be a PITA to remove if I ever have to replace it not to mention removing the oilpan.

So I needed to finish the oilpan by welding in the patch, to get it ready to paint. I used a piece of 2" diameter steel tubing and trimmed the opening to match it. Then I tacked it in place and finish welded it. After grinding, it's ready to go.


http://www.trifivechevys.com/attachment.php?attachmentid=5879&stc=1

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Inside:

http://www.trifivechevys.com/attachment.php?attachmentid=5884&stc=1

[chevynut]

Picked up the engine block today and got it back on the engine stand. They removed the cam bearings, freeze plugs and all oil galley plugs, honed the bores with a torque plate attached, did a "Jet Clean" on it, reinstalled all the plugs and installed a new oil filter bypass valve. Not sure why they had to change that bypass valve. The stand turns a lot easier than it did before, now that I've cleaned off the powdercoating and lubed it up. ;)

My plan is to paint the block and oilpan before I start re-assembly. I'll be spraying them with DP90LF (along with some other parts) then with PPG charcoal BC/CC.

[chevynut]

I masked and primed the block with DP90LF the past couple of days. Did a little hammer and dolly work on the oilpan to fix some shipping damage and a little filling to cover some scratches and dings I couldn't get to, then primed it too. Also sanded and shot the timing chain cover. I forgot to change out the 2.2 tip for the 1.5 or 1.8 tip and got it on a little heavier than I wanted to but it still came out good. :eek:

I'm going to try to shoot the base and clear tomorrow.

http://www.trifivechevys.com/attachment.php?attachmentid=5886&stc=1

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[chevynut]

Anyone know what the boss at the bottom of the 502 timing chain cover is for? It looks like it's ready for a crank sensor. There's a large hole and a small tapped hole that looks like it's for a sensor retainer. Just a curious thing....I don't know of any of these engines that came with a crank sensor from the factory.

http://www.trifivechevys.com/attachment.php?attachmentid=5891&stc=1

[chevynut]

Got the block, oilpan, and timing chain cover painted this weekend. I also confirmed that the cylinders were good to go with the original pistons and after discussing it with the shop I decided to go with file fit rings. It's going to take a little more work but at least I'll know the end gaps are right. Gotta get some more parts ordered now but I should be able to do the final block cleaning and reinstall the crank and rear seal.

http://www.trifivechevys.com/attachment.php?attachmentid=5920&stc=1

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[Troy]

Cnut,

I've always wondered if you need to add some kind of additive that makes the paint more heat resistant. Do you? BTW the paint looks great.

[chevynut]

Everything I've read says automotive urethane is good on engine parts, even heads. I'm leaving my heads bare aluminum. I did put a dab of polyester filler here and there on the oilpan, but I couldn't find anything about the temperature rating of it. I read where some guys were using bondo on engine blocks, so I figured it was okay on the oilpan, and it was a very small amount. Thanks! ;)

[chevynut]

Got the rings ordered from Jegs...Summit had them but said they couldn't ship until 4/21. They lost the sale on that one but I've ordered things from them that they said would take longer and they showed up pretty quick. Just didn't want to wait this time. I still need to order a ring compressor from Summit...probably going to get one of the non-adjustable ones. I thought for sure I'd find a used one on eBay, but haven't yet.

When I get all the parts I plan to start assembly. But I need to do some final cleaning on the inside of the block. Any specific recommendations for that? I've heard to scrub the bores with soap and water, then oil them. The shop did a "Jet Clean" but I'm not sure what that means. All the oil galley plugs are installed.

[rockytopper R.I.P 5-13-2017]

Nice last time I saw a ramjet BB in a trifive it was a 55 ht at Good guys and had a 175,000 dollar price tag marked on the window and the words for sale were crossed out with SOLD if that makes you feel any better about your investment lol. But they may have spent 300 getting it built lol....

[Rick_L]

Same day that you are going to start assembly, roll the block out in the driveway and wash it with soap and water. Remove the oil galley plugs first. Then dry with air, and thoroughly blow the water out of all the oil passages. You could spray it it WD40 (not oil) but since you're going to start assembly that day it really isn't necessary. Don't use any oil until assembly starts.

[chevynut]

I thought about telling them to leave the oil galley plugs out and let me install them. Just a little more work now.:p

[chevynut]

They forgot the CAM! :D

I found this Mobil Oil article on engine cleaning and assembly and read through it looking for tips and details I'll need to consider. It's been a long time since I assembled an engine, besides the one in my Grizzly. It's not a bad article and has some good thing to watch for. One thing I was looking for was when the cam should be installed. It seems like it would be easiest to install it even before the crank is installed, since you can actually guide it in the bearings from below. Anyhow, I finished reading the series and realized they didn't even discuss the cam and timing chain/cover installation. I wonder if that's a oversight or what. ;)

I know the cam can be installed even after the heads, but when is the best time in the build sequence to do it? I still haven't decided if I'm going to change mine or not. :confused:

https://mobiloil.com/en/article/car-maintenance/car-maintenance-archive/how-to-assemble-an-engine

[Rick_L]

I install the cam either just before or just after I install the crank, usually first. First is good, being able to see it is helpful to guiding it into the bearings.

But it really doesn't matter and you make adjustments. Sometimes what you're checking and measuring as you assemble makes a difference in the order. On an engine that possibly has some adjustments to make, there's a trial assembly prior to the final assembly. Which might require cleaning the block twice. The trial assembly might not use every piece. Every time you assemble there is some different factor that you need to take care of or account for.

[chevynut]

On an engine that possibly has some adjustments to make, there's a trial assembly prior to the final assembly. Which might require cleaning the block twice.

I'm not going to go to those lengths ;). Keep in mind this was a NEW, FACTORY ASSEMBLED crate engine when I bought it. It wasn't a used engine, and it had no machine work done on it (except honing). I'm assuming everything was checked during assembly at GM and I don't need to do much more. I'm using the same bearings in the same locations, the same pistons in the same locations and the shop fitted the pistons to the bores for me when honing with a torque plate. They're a reputable shop an I think I trust them without re-checking clearances (and I don't have a torque plate). They replaced the cam bearings with new ones and nothing I've read says it's critical to check them.

All I'm replacing is the rings, seals, and possibly the cam and rockers. I may mic or Plastigage the bearings just to be safe, but I have no reason to suspect anything is wrong. I could have just fired this engine up when I got it. :)

Is it unreasonable to expect that it was assembled correctly to begin with? What all should I need to check? I'm not trying to blueprint it. I've even decided that balancing is probably a waste of money with a redline below 6000 RPM and a factory balance.

One thing I'm not sure how to deal with is the heads. I know they have some junk in the ports, and I'm afraid I may have to disassemble them to clean them up. I don't know how else to ensure they're clean and avoid sucking stuff into the cylinders. So then what? Do I change the valve seals? I have no reason to suspect they're bad. The springs are capable of accepting a much larger cam. Everything is new.

[chevynut]

I was reading through this article, and some of the stuff I really question. I know it doesn't apply to Chevy engines in particular, but what do you guys think about it?

http://www.mustangandfords.com/how-to/engine/mufp-0610-engine-building-mistakes/

"Dynamic balancing is crucial to engine smoothness and survival because vibration (any vibration, no matter how small) kills. It shakes things to pieces. Not balancing an engine is foolish, courting disaster at worst and shortening engine life at best."

"Do not roll rings into grooves (even though everyone does it). It is impossible not to warp piston rings when you roll them on because they are not spring material. They will remain warped."

"Absolutely never lay a crankshaft on its side-not even for a few minutes. Crankshafts should always be stored standing straight up or hanging from a storage fixture. Laying a crank on its side will cause permanent damage."

[NickP]

FORD?!!!! Well, the crank they are cleaning is junk, it's on its side in the cleaning tank. Not balancing, again, a ford.

[chevynut]

FORD?!!!!

Don't know why it matters...same engine building processes and procedures apply. Maybe their cranks bend easily. ;)

[Rick_L]

Your engine was balanced at the factory. No need to re-balance it.

Your crankshaft is not cooked spaghetti. It's ok to lay it on its side.

Some will tell you that you need a ring expander tool (just a pair of pliers with tips to grab the ring end gap) to open the rings to assemble them on the pistons. I never used one on race engines because those rings are back cut, thin, or both, and they're not as stiff as stock rings. You probably don't need them for a one time deal. Just don't twist the crap out of them. It's pretty easy to twist the ring a bit with the pliers too. But you really have to screw up to yield it causing a permanent twist, even with no tool.

Whoever wrote that crap is a magazine writer not an engine builder.

[markm]

Whoever wrote that crap is a magazine writer not an engine builder.


And probably trying to sell advertiser's tools.

[55 Rescue Dog]

All you need to put rings on, is this simple $7 tool. Works great.
http://www.amazon.com/Lisle-33500-Piston-Ring-Installer/dp/B0009OMYC4/ref=sr_1_1?ie=UTF8&qid=1460065599&sr=8-1&keywords=piston+ring+expander

[chevynut]

I have a pair of ring pliers, so I'll be using them. The "warping the crank" BS is just dumb. A thick piece of steel like that doesn't bend that easily. And the rings don't stay bent unless you bend them past the yield point. I'd be more worried about scratching the piston than warping the rings. Yeah, those Ford guys seem pretty stupid. LOL :) :)

[chevynut]

One thing I'm not sure how to deal with is the heads. I know they have some junk in the ports, and I'm afraid I may have to disassemble them to clean them up. I don't know how else to ensure they're clean and avoid sucking stuff into the cylinders. So then what? Do I change the valve seals? I have no reason to suspect they're bad. The springs are capable of accepting a much larger cam. Everything is new.

Any advice on the above? It will be a little while before I get to that point, but I want the heads ready to bolt on when I get the pistons in. How hard is it to disassemble the heads myself if needed? If I could just get the valves open a little, I could clean the ports out with a sprayer and solvent.

I got the head gaskets and ring compressor ordered from Summit, so the only thing I can think of that I still need for assembly is a cam and rockers, if I intend to do that upgrade. Oh, and I'll probably need intake gaskets once I figure out how I'm going to finish the intake manifolds. Got right at $600 in it so far.:eek:

[55 Rescue Dog]

There is only one way. Just get a spring compressor, and simply take them apart.
My "new" LT-1 that had sat for 37 years, that's what I did, with new seals. Wasn't too concerned about any valve springs compressed forever, because the rockers were loose. So, especially if changing the cam, it should come apart for new springs anyway.
I wish a had a dollar for all the freakin tools I have only used once.

[chevynut]

There is only one way. Just get a spring compressor, and simply take them apart.

That's what I was concluding too. If there was an easy way to open the valves I think it would work fine, but there doesn't seem to be.


So, especially if changing the cam, it should come apart for new springs anyway.

The stock springs are fine for a new cam. They can handle up to .675 valve lift according to GMPP. They have 140 pounds on the seat at installed height.


I wish a had a dollar for all the freakin tools I have only used once.

I'm probably going to find someone to borrow a valve spring compressor from.

[Rick_L]

You need about 350 pounds on the seat with the solid lifter cam I have chosen for you.

You will need to disassemble the heads to do the CNC porting anyway.

[chevynut]

Funny. ;) :) :)

[markm]

who gives a shit its a show car, Cnut probably has the reaction times of a turtle.

[Bitchin'57]

who gives a shit its a show car, Cnut probably has the reaction times of a turtle.
He might have a point. How much horsepower do you need to putt-putt through the show field? :p

[chevynut]

who gives a shit its a show car, Cnut probably has the reaction times of a turtle.

Mark, I'll bet my reaction time is as good as, or better than yours. Maybe we ought to play "slap the hands" someday. I didn't build a drag car, it's pro-touring if you understand what that is. Too bad you can't drive that single purpose strip car of yours on the street or on the twisties, because I'd blow your ass away in autocross. LMAO! :)

[Fladiver64]

I think the challenge with getting the valves open is how to bolt the head down. On race cars we used an on car valve spring tester, that was basically a lever that locked around the locker and allowed you to open the vales to test the spring pressure. I am sure you could make a simple lever to to the same thing as long as the head was bolted to something that will not move. The other option is if I was taking the valves out I would replace the valve seals just because I dont like to re install old seals even if they are new. If you bought the seals from a chain auto parts store (get the brand you want) most of them have spring compressors on their free loaner tool wall.

[chevynut]

The other option is if I was taking the valves out I would replace the valve seals just because I dont like to re install old seals even if they are new.

I was afraid someone would say that. :( I checked out the seals I took out, and both the rear main and front crank seal look perfect. They're soft and pliable, even after over a decade of sitting. I'm replacing them anyhow, because they're cheap.

I don't know a thing about valve seals except that they keep oil from passing down the valve guide. What kind (brand, construction) are best in case I decide to change them? Looks like they're relatively inexpensive too.

[markm]

It always makes me laugh when people who have never done it think reaction time are easy. It is a lot more than the human factor that goes in to it. I have a Z28 and a Corvette if I desire to go auto crossing.

Bitchin57 you get my point.

[chevynut]

It always makes me laugh when people who have never done it think reaction time are easy. It is a lot more than the human factor that goes in to it. I have a Z28 and a Corvette if I desire to go auto crossing. Bitchin57 you get my point.

I really don't care about drag racing. I guess you don't know how to stay on topic either.

[NickP]

I was afraid someone would say that. :( I checked out the seals I took out, and both the rear main and front crank seal look perfect. They're soft and pliable, even after over a decade of sitting. I'm replacing them anyhow, because they're cheap.

I don't know a thing about valve seals except that they keep oil from passing down the valve guide. What kind (brand, construction) are best in case I decide to change them? Looks like they're relatively inexpensive too.

Trying to stay on point, what "valve stem seals" do you presently have? I always thought this was a misnomer anyway. The device, be it an o-ring, bonnet or a perfect circle type simply acts as a diverter rather than a true seal. Having said that, the PC units do come closer to a true seal due to the fact they are stationary for the most part. The others simply ride up and down with the stem movement. Also, if you change things, give consideration to valve lift (more) and a possible clearance issue at full open. If it interferes, you will destroy the seals and end up with all of that trash in the engine.

[chevynut]

Trying to stay on point, what "valve stem seals" do you presently have?

The current seals are the stock ones that came in the heads....GM part # 12495690 (seal kit). The kit seems to contain 16 of the 12550422 seals that look like this:

http://www.jegs.com/images/photos/800/809/809-10212810.jpg
Summit shows these as a replacement: http://www.summitracing.com/parts/cca-503-16 or http://www.summitracing.com/parts/cca-529-16

http://static.summitracing.com/global/images/prod/mediumlarge/CCA-510-16_ml.jpghttp://static.summitracing.com/global/images/prod/mediumlarge/CCA-529-16_ml.jpg



the PC units do come closer to a true seal due to the fact they are stationary for the most part. The others simply ride up and down with the stem movement.

Hmmm, it's my understanding that these clip into a groove on the valve guide. So they're stationary as far as I know.


Also, if you change things, give consideration to valve lift (more) and a possible clearance issue at full open. If it interferes, you will destroy the seals and end up with all of that trash in the engine.

I won't be doing anything radical if I change my cam, but I'll keep that in mind. Thanks.

[55mike]

Although I don't own the ZZ502, I have a close friend who does (his is the FI with an Accel computer). From what I observed with the stock cam, that thing is not too bad. Has a nice rump, and plenty of bump. So, I'm thinking you don't need too much more than what comes in the ZZ502 for what you are doing..

[chevynut]

Thanks for the feedback Mike. I was looking to gain just a little HP into the 550 range if it was easy and I didn't give up much if any low end. To me the most important part of the range is 3000-5000 RPM. The small TB limits airflow at much over 4000 from what I can see, so my 1000 CFM TB should help some there. I just didn't know if the cam is the limiter.

What's surprising to me is that Comp Cams has a program to select cams, and it chose a cam with less duration and less lift than the stock 502 cam as the "best choice" for a hot street engine.

[Rick_L]

Starting sometime in the 90s, Chevy started using what I call the "positive" type seals which you showed in your post. (As opposed to the other styles that Nick mentioned.) These should be as good as it gets. These did not fit when they used single springs with flat wound dampers. They apparently decided after 40 years of study that having the seal and no damper was better than a damper and no seal other than the o-ring which is just an anti-drip deal.

It's fairly easy to nick the seal and not notice it. Some of these seals come with a little cellophane cap to put over the valve stem which keeps the seal from being nicked by the keeper groove or the o-ring groove when you install them. It's not really useable for removing the seal though. When I've used these seals on a race engine, I always re-use them a bunch of times, but on a street engine I'd replace them if I ever tore down the head.

Over the years for race stuff, the shops I've done business with have had a mixed approach to seals. Some are highly in favor of them, others not so much, saying that oil control is a tight valve stem to guide fit. There's also shops that put them only on intakes, which also makes a lot of sense.

[chevynut]

Thanks for all the info. I think I'll probably just fork over the few bucks for new ones when I re-assemble the heads. I see they're made of Tefon or Viton. I'm familiar with both materials, but which is better for valve seals? Sounds like this isn't a really big deal if you can actually run without them.

[Rick_L]

Viton is actually a better material for this IMO. Teflon would probably be better for high temp that one wouldn't see. To me though that's splitting hairs.

As you say it's a case of do you have them or don't have them, not which ones.

[chevynut]

I've stayed away from the forum for the past couple of weeks trying to get some stuff done and learn more about cams and valve springs. I've finished Chad's front C4 clip install, finished another C4 frame, and got my 502 partially back together. I've been working on the clutch and bellhousing parts too.

After painting the block, I washed the bores with soap and water, and oiled them. I gapped the rings to .022" per Total Seal recommendations and put them in baggies marked for the cylinders they went into. Their instructions say .0045" per inch of bore so I calculated .020", but after calling them about the first and second ring gaps being the same, they said to gap them both at .022". Most guys say to make the second ring gap larger than the top ring gap, but Total Seal doesn't follow that philosophy.

I washed the crank in solvent and cleaned the oil passages with a brush, even though the engine is new. I measured the crank journals and bearings with a micrometer and snap gauge and verified that I have acceptable clearances, then installed the crank and rear main seal. With the crank installed and main caps torqued to 110 ft-lb using ARP Ultra-Torque lube, I checked the crank end play and found it to be acceptable at .007-.009".

Next I removed the stock rings from the pistons and found something interesting. The second ring on one piston had about 1/4"-1/2" broken off the end of it. I was having difficulty removing it with my ring pliers and didn't understand why until I looked closely and noticed it was a lot wider than the others, and had a rough end. I know it didn't happen when I removed the pistons, as I found no pieces. I sent the pistons with rings to the machine shop, but as far as I know they only measured the pistons and honed the bores to fit and didn't mess with the rings. So I have to assume the ring was broken from the factory. Glad I found out now.

I installed the new rings on the respective pistons and set the gap orientation per Total Seal's recommendation. The Powerhouse Products tapered 4.470" ring compressor made it really easy to install the pistons in the block. I installed each piston after lubing the piston, pins, and rings with 10W-30 oil, but I didn't put assembly lube on the rod bearings yet. I checked the rod bearing clearances (after previously measuring the journals) with green Plastigage and found then all to be between .0015 and .002". After checking the clearance of each bearing, I cleaned off the plastigage with solvent, applied assembly lube to the bearings, and tightened them down. Once they were all checked I torqued the rod caps to GM specs.

I can't button up the bottom end until I get the timing chain cover installed, which means I have to get the cam issue resolved.

[chevynut]

I borrowed a valve spring compressor from a friend and today I removed all the valves from the heads. After previously cleaning the heads, I'm glad I did this. I found a lot of "trash" between the valves and seats that the solvent washing didn't remove.

Interestingly, I found that the springs were all shimmed from the factory. The intakes all had .062" shims, and two of them had an additional .0175" shim. Every exhaust spring had one .062" shim and a .032" shim. I guess steel shims or spring seats are needed on an aluminum head to prevent wear.

I measured the free length of the springs at 2.430-2.450" (#1 cylinder, Intake and Exhaust). Then I measured the head to retainer height with a snap gauge and micrometer at 2.040-2.043" (#1 cylinder, intake and exhaust). Not sure how accurate that is, so I may need to buy a spring mic.

These valve springs are spec'd by GM to have a seat force of 140 lb at 1.940" installed height and 368 lb/in per my 2001 GMPP catalog. Now, let's look at what we actually have. I have ordered a spring tester to verify the springs, but a quick look at the specs says something is screwy.

For the intake valve on #1 cylinder, the spring is 2.430" long (measured with digital caliper). Including the .062" shim, the installed height is 1.978". The specified installed height is 1.940". At this installed height the spring is compressed .452" and should have a seat load of 166 lb. The GM spec on the seat is 140 lb.

For the exhaust valve on #1 cylinder, the spring has a free height of 2.450". The head to retainer height is 2.043" and the shim stack is .094" tall. So the spring installed height is 1.949", close to GM spec. The spring is compressed .501" and should therefore have a seat force of 184 lb against the 140 lb spec.

I've read that the stock 502 hydraulic roller lifters don't like over 150 lb of seat force, or they make noise. The seat loads I calculated from the factory are higher than that.

Then there's the specs that Jegs and Summit have for the EXACT same springs, GM P/N 12462970:

http://www.summitracing.com/parts/nal-12462970
http://www.jegs.com/i/Chevrolet+Performance/809/12462970/10002/-1

Curiously, they say the spring rate is 325 lb/in.

Howard's Cams has what I believe is the same spring (1.514" OD, dual, no damper) and specs a 360 lb/in rate.

http://howardscams.com/i-24078564-howards-cams-98512-1-performance-1-514-dual-valve-springs.html

These are BIG discrepancies and I won't know what I really have until I measure the springs themselves.

After everything I've read about valve springs, this is far from a science and everyone has an opinion. Some say you need 200 lb on the seat to prevent bounce, and 450+ lb for a high performance BBC cam to prevent valve float. I've read where guys have claimed to encounter valve float with a stock zz502 (same longblock as a Ramjet 502) at 5700-5700 RPM. Chris Straub has told me that my stock valvetrain can handle a .620" lift cam at 6000 RPM. The opinions are all over the place, and perhaps the way these engines are set up explains why. It seems like they just get close and call it good. I even read an article that said GM uses low valve open forces to control maximum RPM their crate engines will see, and EXPECT valves to float at the specified maximum RPM.

Chris Straub tells me he has done "a few" 502s and has gotten 620 ft-lb and 610 HP and peak torque at 4500-4800 RPM with a 7% drop at 1000 RPM on each side of the peak with the cam he's recommending to me. He says an "altitude cam" needs moderate lift and short duration. I don't know all the specs but the lift he recommends is .620" intake and .580" exhaust and he's recommended a 6 degree split. I'm very skeptical of that working with my stock valvetrain and I can see thing snowballing fast. Plus, after looking at dozens of cams and talking to half a dozen companies I don't think .620" is moderate lift for a BBC hydraulic roller cam.

So I'm still trying to decide on whether or not to do a cam change. I'm not sure who to believe or trust. I have talked to half a dozen cam manufacturers and there are some common elements to their recommendations but some are further apart. I really question whether Straub's claim that my stock valvetrain will work to .620" is valid, and over .600" the lifters start to drop below the top of the dogbone lifter retainers and could cause them to lift. Some guys recommend a taller lifter for this reason, but that adds even more weight. A custom Straub cam is $575 on a SADI core and a Howard's custom cam is $350 on a billet steel core. Money is not a big deal, but I want to do this once and the Howard's cam would give me new springs and retainers for the same price as the Straub cam. I feel like some of these cam guys don't understand that not everyone is looking for every horsepower they can squeeze out of their engines. I've tried to make my objectives very clear to all of these guys.

As of now, I'm thinking I need a cam in the .575"-.600 lift range with around 230-234 intake duration and a 6 degree split I/E (236-240 E). This is based on the recommendations I've gotten so far from Lunati, Howard's Cams, Comp Cams, Bullet Cams, and Chris Straub plus all the articles and forum's I've read on the 502 upgrades. Everyone who has recommended a specific cam says I need a 112 LSA and ICL varies from 106-110 degrees. I think an early intake closing is important at my altitude and 9.9 CR. I wanted to discuss this with the "cam expert", UD Harold from Ultradyne (now owed by Bullet Cams), but unfortunately he passed away last year. I'm still waiting for a reply from Crower and Crane, then I'll decide which way to go.

This sure has been a learning process for me.

[chevynut]

I also machined a stock GM pilot bushing to fit over my Viper T56 input shaft which is .750" diameter. I'll have to install it when the engine comes off the stand.

http://www.trifivechevys.com/attachment.php?attachmentid=6000&stc=1

[Rick_L]

I agree with you that 0.620" lift is not so "moderate" for a street engine.

What do you have for rocker arms?

Springs are a deal where you might get differing results from what is claimed to be the same ones from set to set. That's why on a precision build you always measure the actual installed seat force.

The question of how much seat force with a hydraulic cam is too much is an interesting one. A friend is considering going to a hydraulic cam on a 468 BBC - and he's been asking that same question without consistent answers. This after breaking a solid lifter. More valve spring force will always control the valve better. The question is whether the roller/needles are going to wear with more seat force - or is less spring force going to cause the valve to float/bounce which is even worse on the lifter? Interestingly, I talked to a guy at the races this past weekend who said he's turning 7800 rpm with a stock LS7 lifter that's "shimmed up". He didn't offer any details on the shimming when asked. I don't know what's unique about an LS7 lifter either.

Straub is selling you his "expertise" in addition to the cam. He talks a good line but I don't know how good (or bad) his stuff might be. Remember this, as I've been saying - once you get in the proper target range on the cam specs, the difference between all of them is splitting hairs.

[chevynut]

Well I finally heard back from everyone I asked about a cam recommendation. I gave every one of these companies the EXACT same specifications and goals for my car. I told them I was at 5000 feet and wanted to bump up the torque across the RPM range and keep a broad range like the current cam. I don't want a race cam or anything too "peaky" either. I told them all it was a street application with no drag racing intended.

Comp Cams: XM284 .547/.547 230/236@.050" LSA 112 ICL 110

Lunati: 20010721 .575/.575 221/229@.050" LSA 112 ICL 106

Howard's Cams (custom): .585/.585 231/241@.050 LSA 112 ICL 108

Bullet Cams (custom): .567/.567 230/234@.050" LSA 112 ICL 107

Crower (custom): .550/.550 220/229@.050" LSA 114

Chris Straub (custom): .620/.580 no other specs. "I have done a few of these with cam only change and they end up 610HP and 620#/ft of torque. Peak HP is at 5800-6000 rpm and peak torque is around 4500-4800. Torque band looses only around 7% from peak 1000 rpm below and 1000 rpm above the peak. That would put you at around a minimum of 576#/ft for 2000 rpm." "Altitude cams are short duration and moderate lift. We will need to be around .620” lift on the intake and .580 on exhaust. The stock stuff will take a max of .620”.

Crane: "We don’t have a camshaft that will increase HP without having to turn more RPM. The only way to accomplish that feat is by installing a higher ratio rocker arm, like our 1.8 ratio #13755-16, to help take advantage of the flow capabilities of the cylinder heads. You will need to check your valve springs to see if they can handle the extra lift @.558” int., and .576” exhaust or install our #99832-16 springs with #99976-16 retainers."

But Crane did just what I want to do here so why do they say it can't be done?: http://www.superchevy.com/how-to/engines-drivetrain/1412-how-to-install-a-crane-cam-on-zz502-little-bit-o-boost-part-2/#photo-14



So I see some common things here, with Crane and Straub being outliers. Straub didn't mention anything about the dogbone issue, and that bothers me if he's set these engine up before. He seems to want to push the Morel lifters and he recommended them to me. But they add a lot of cost. Also, I just don't believe the stock springs are good for .620" lift based on what everyone else says. So I'm really skeptical about going that route.

Crane seems way out there if they can't even recommend a cam to me. I don't want to go with 1.85 ratio rockers because I want to keep my valve covers. And I don't see what they gain me that a cam change won't. And I just bought some COMP Magnum roller tip rockers with 1.72 ratio.

I've looked at other timing events based on the specs they gave me above. The COMP cam is advanced 2 degrees, the Howard's 4, the Bullet 5, and the Lunati 6 degrees. More advance gives better low end torque. The Lunati has the earliest intake closing (based on .050" duration) followed by Bullet, then Howard's, then COMP. I know there's only so many degrees in a circle to play with. ;)

[Rick_L]

I had no idea that the "lead free" movement had extended to engine bearings, but it's not a great surprise. On the other hand, I can't see that the "unleaded" bearings could last a typical engine's lifetime if they couldn't live for a few dyno pulls with some extra power. Yeah, I know they had a blower on it.

I assume that you'll now get some good bearings as part of the project.

I don't know how the OEM "dog bones" work, but what they say seems pretty simple and direct. One of those fails, and you won't have anything useable but an intake manifold if it occurs at high rpm. And it could fail at idle too.

All your camshaft choices are the same cam except for the Lunati and Crower, which are a bit milder.


We don’t have a camshaft that will increase HP without having to turn more RPM.

True statement unless you get a blower.

[chevynut]

Here's what Crane sent me when I asked how increased the entire torque curve on that engine in the article....

"At 5000 ft elevation, you only have an effective compression ratio of 8.6 to 1, which will not support a cam with more duration. The rocker arms will increase lift without lowering cylinder pressure."

So they're saying only lift matters, not duration, as I have suggested before. I can get higher ratio rockers or a cam with more lift. Since I am considering changing the cam anyhow, what advantage is there to the rockers? They cost more than a cam at $416 and force me into another set of valve covers.

I question this Crane guy's knowledge. Cylinder pressure is affected by intake closing timing not just intake duration. My current cam closes the intake at 75 ABDC based on advertized duration, and 40 degrees ABDC based on .050" duration. Seems like the advertised is what matters since pressure will escape with any sized hole.

So in my mind, a cam with an intake closing event earlier than 75 degrees should help my power by keeping cylinder pressure higher. The Lunati cam closes at 60 degrees, the Howard's at 70, the COMP at 72, and the Bullet at 76 ABDC.

Based on all this, the Howard's cam seems like the best compromise, except I think the exhaust duration may be a bit long. Straub says there should be a 6-8 degree split. The Howard's cam has more lift and intake duration is 231 which is a little more than I have now. It's a custom grind so they can probably change the exhaust side for me if I want to.

Then the Crane guy says "You will need to check your valve springs to see if they can handle the extra lift @.558” int., and .576” exhaust or install our #99832-16 springs with #99976-16 retainers."

I gave him my valve spring specs, so why can't he tell me if they'll work? They can handle the lift as far as coil bind. The springs he recommended are beehive springs at $364 then I need new retainers and locks...to get a little more lift. And Straub says he wouldn't use beehive springs on any BBC with a heavy valvetrain. If one breaks, your engine is toast.

[Rick_L]

I've never run beehive springs so I can't comment on that except that if it breaks, being a single coil, you're going to drop a valve.

The first thing I would recommend to you on the springs is to check them and see if they are anywhere near spec. You might be surprised. What I see in your last few posts is that they might not be what you expect.

Keep in mind that a higher ratio rocker will add a little bit to the duration. Going to a full roller rocker arm has more benefits like strength and durability - but it's not cheap.

It finally dawned on me why you want small duration/high lift at elevation.

[chevynut]

I got my spring tester and I guess I now understand why they call it "spring pressure", because that's what you're actually measuring with these tools. They have a hydraulic cylinder and a l" area piston in them and they attach a pressure gauge to it. As the fluid is compressed, you measure pounds per square inch. Spring "pressure" is actually a misnomer, as springs don't exert "pressure" they exert force.

Anyhow, I checked all of my springs today. I first checked them at 2" including the .107" thick retainer because they're dual springs. Then I checked them at 1.5" height with the retainer. I used those measurements to calculate spring rate.

The free height of the springs averaged 2.537" with the retainer.
The 2" measurement average was 156 pounds with a min of 150 and max of 161 and standard deviation of 4.1 pounds.
The 1.5" measurement average was 332 pounds with a min of 325 and a max of 345 and standard deviation of 4.8 pounds.
The spring rate average was 352 pounds per inch with a min of 336 and max of 372 with a standard deviation of 10.1 pounds per inch.

I calculated the spring load ("pressure) at the specified 1.94" installed height and the average was 139 pounds with a standard deviation of 4.3.

The GM spring spec is 140 pounds at 1.94" installed height and a spring rate of 368 pounds per inch. So the load at installed height averages pretty close to spec but the rate is a bit low.

I think you can get within about 5 pounds with this tool, but it's a little tricky. It would have been better if they had a positive stop on the micrometer, and let the piston move within it. Instead, the micrometer moves with the piston and you have to press down until you can't turn the micrometer so there's a little "feel" involved. I probably changed that "feel" a little as I got used to it and my measurements got better. It may have affected the average by 3 or so pounds.

One thing I'm not sure about is the shims that were under each valve, and if they are included in the installed height of 1.940". Since the heads are aluminum, I assume you need at least one shim to keep the spring from digging into the head so it probably includes the shims. I ordered a spring micrometer (yet another new tool :rolleyes:) to be able to accurately measure the installed height. I have a set of snap gauges and micrometers, but they seem to be difficult to get a good measurement. I know they say you only need to be accurate to around .020" but the spring micrometer is relatively cheap and will make the measurement a lot easier, faster, and more accurate. I doubt GM actually went to all this trouble when they built this engine. ;)

Here's the spring checker tool I got:

http://static.summitracing.com/global/images/prod/mediumlarge/pro-66841_ml.jpg
And here's the spring micrometer:

http://static.summitracing.com/global/images/prod/mediumlarge/pro-66902_ml.jpg

[Rick_L]

That kind of checking tool, while not a total waste, is not the most accurate one on the planet. In addition to all the things you mention - it uses a cheap hydraulic pressure gauge which is rarely accurate to any kind of precision. But while not well calibrated, it does give you relative results. A valve spring tester like a "Rimac" is a better tool. (Google it.)

Installed height, in race engine/valvetrain lingo, does not include any shims. What you will find is that the available space for the spring and shims varies wildly on most applications because there are many variables. The biggest ones are how deep the spring seats in the heads are machined, and the height of the valve seat compared to "stock". Almost always the available height is greater than the recommended installed height - which requires shims.

Your spring height micrometer is a nice tool, more precise. It's not necessary, but makes things easier and thus more repeatable. A snap gauge will do the job just fine in most cases.

Just like the available spring height is often greater than expected, spring tend to have less force than expected. Either one means shims to get seat force up to spec.

Running a high force spring directly on an aluminum spring seat means that you'll probably get erosion of the aluminum. What I like to use is a hardened spring cup that has a small flange on it. The spring cup is about .060" thick and the flange is about .060". Which means your spring seat in the head needs to be about .120" larger than the spring. Aftermarket heads usually are already machined for that, but probably not factory heads. Shims can be stacked over or under the cup. With no cup, you need steel shims, and put a thick one next to the spring. An .015" shim will often get bent up.

[Bitchin'57]

At your altitude, I'd go with a high lift, short duration cam, so I'd pick the Lunati. In a 502 sized motor, it will sound pretty smooth, but, it will have lots of low end grunt. Since you won't be drag racing it, you're not concerned about high rpm power.

[chevynut]

That kind of checking tool, while not a total waste, is not the most accurate one on the planet. In addition to all the things you mention - it uses a cheap hydraulic pressure gauge which is rarely accurate to any kind of precision. But while not well calibrated, it does give you relative results. A valve spring tester like a "Rimac" is a better tool. (Google it.)

Yeah I've watched videos where they used the Rimac. It's a $700+ instrument (not even available at Summit) and I'm not going there. They're $600 used from what I've seen.

I was told just to take my springs to the local machine shop and have them checked...they're not going to do it for free. Then if I need new springs I'd have to have them checked again. I likely won't be doing this again anytime soon, if ever. So the $104 tool seemed like a reasonable investment. I personally think the gauge is fairly accurate, and it's probably accurate to 5 pounds or less. It shows 10 pound increments and you have to estimate between the marks. At least I think it's repeatable if a guy could calibrate it. As I said, it would be FAR better if it had a positive stop instead of the way it's designed.

I watched some videos that said you only needed to get spring height measurements accurate to .020". That means you could be off by 8 pounds. So this stuff doesn't seem to be an exact science anyhow.


Installed height, in race engine/valvetrain lingo, does not include any shims.

Interesting...so with the .062" shims on the exhaust valves and .094" of shims on the intake valves the seat force would be WAY over the 140 pound spec if the installed height without shims is 1.940".

I guess I'll have to see what the installed height is after I get my micrometer.




Your spring height micrometer is a nice tool, more precise. It's not necessary, but makes things easier and thus more repeatable. A snap gauge will do the job just fine in most cases.

I tried it with the snap gauge and it's just hard to get it in there and make sure it's perpendicular, etc. And the retainer has to be perfectly seated. So the micrometer should be better and it was only $50.



What I like to use is a hardened spring cup that has a small flange on it. The spring cup is about .060" thick and the flange is about .060". Which means your spring seat in the head needs to be about .120" larger than the spring.

I saw some seat cups that locate off the ID of the springs. They may work well for my application if I can find the right size.


With no cup, you need steel shims, and put a thick one next to the spring. An .015" shim will often get bent up.

Thanks for that tip.

I saw this video the other day and it was just amazing to watch:

https://www.youtube.com/watch?v=_REQ1PUM0rY

[Rick_L]

I knew the Rimac was expensive but it's gone up a lot since I got mine. The micrometer is cheaper than I remember them.

One thing you might do is get a couple of springs checked on a Rimac as a crude calibration of your tester.

[Troy]

Wow that video was scary, it's a wonder these engines stay together. I'm always amazed when I think that at 6000 rpm that piston is going up and down 100 times per second!!!! How does it not fall a part or weld to the cylinder?!?!

[chevynut]

One thing you might do is get a couple of springs checked on a Rimac as a crude calibration of your tester.

Yes that would be a good thing to look at when the time comes. I know COMP and others sell "calibration" springs with a known force at a given compression. The hardest thing on this tester is getting it to sit flat and compressing it to the right level. I made a "pusher" for my drill press and put it in the chuck. Then I set the spring on the table and put the tester over it. Pushing down on it you have to stop when the dial just stops turning so there's a little "finesse" involved. But you're probably accurate to .010" or less.

[chevynut]

Rick, do you know why Straub says a 502 should have a "6-8 degree split" between intake and exhaust duration? Whats the effect if that increases or decreases?

Also, I noticed that some manufacturers use the same intake and exhaust lift while many others use a higher exhaust lift. Is that because the exhaust valve is smaller? I didn't think that was an issue since the exhaust was forced out of the cylinder by the piston. Straub actually recommended a .620" intake and .580" exhaust lift for me which is reversed from what I typically see.

I found this:

http://speedtalk.com/forum/viewtopic.php?f=1&t=6529

"Low compression or intake restricted engines where the torque in the mid-range is much more important than the few horsepower at the top is pretty common practice for a camshaft like this; only SLIGHTLY smaller on the exhaust side though."

"For me,not usually working on V8's or US engines,seeing an exhaust lobe with more duration and lift than the intake is unusual... 99% of all European and Japanese engines I've laid hands on has longer duration and more lift on the intake lobe than the exhaust.. So what's "unusual" I guess comes down to the type of engine one's dealing with."

I think I've pretty much studied this stuff as much as I want to :) and I'm pretty sure a cam change is what I want to do to improve high altitude performance....if only for bragging rights. :) :)

[chevynut]

I think I'm honing in on a cam spec based on all my reading...as well as a supplier. I'm probably going with Howard's Cams. Summit sells them and every forum I've looked at the customers say they make really good stuff. They've been around since 1945 and their prices and quality seem to be excellent. Their hydraulic roller cams are all made on billet cores and are parkerized, which some other suppliers don't use or charge an arm and a leg for (Crane).

"Crafted from the finest grade race-quality billets, your Howards Cams special grind camshaft will be manufactured on high-precision cam grinding machines. All hydraulic and mechanical flat tappet camshafts will be 100 percent Rockwell checked and parkerized, ensuring a hard, wear-resistant quality. To protect all of this excellence and be certain that your special cam reaches you in nothing less than perfect shape, your cam will be packed and shipped in one of Howards Cams' unique, high-impact plastic reusable cases."

This is the specs I'm looking at:

.589/.601" lift (.596/.608 with 1.72 rockers)
229/235 duration @.050"
282/288 advertised
112 LSA
107 ICL
Intake closes 42 ABDC
Exhaust opens 55 BBDC
5 degrees advanced

This is almost EXACTLY the same as Howard's off-the-shelf 120326-12 cam with the exception of the ICL, as it uses a 108 ICL and has an intake closing of 43 ABDC and an exhaust opening of 54 BBDC. A custom grind from Howard's is only $14 more than an OTS grind so cost is not an issue. I will probably discuss this with them before ordering. I don't know if 1 degree of advance makes much difference, but I see cams with a minimum of 4 and maximum of 6 degrees advance so the range is small.

I think the intake closing timing is important for my 9.6:1 compression ratio and altitude. The earlier intake closing builds more cylinder pressure and the additional advance increases torque. Most of the Crane cams I've looked at have 5 degrees of advance.

One question is whether I'm going overboard on lift based on what my heads can support. I'm not sure how to figure that out.

And here's one thing that bothers me...Howards describes this OTS cam as:

"Lift: .589 / .601, Duration @ .050: 229 / 235, Centerline: 108, Fair idle, Moderate street/mild bracket, Good mid-range, 10.0 - 11.5:1 compression & 2500+ stall converter."

Why would it need higher compression?? And it seems like the moderate 8 degrees of overlap @.050" and relatively short duration would give better than a "fair" idle. I don't know what "fair" means to them. My current cam has 9 degrees overlap at .050" and the one Howard's actually recommended has 12 degrees due to the longer exhaust duration.

I need to make sure I'm not going to run into any trouble with the lifter "dogbones" with that much lift. Chris Straub seemed to think I was okay at .620" and Howard's said I should try to stay under .600" so I should be okay.

So who determines what springs I need now? Does the cam manufacturer spec them or do I guess? :(

[Rick_L]

Last things first. The math of camshaft lobe detail once the duration and lift specs are chosen is well established. It's in a first level kinematics course which many undergraduate engineers take. Computers make achieving it even more convenient. Same with the manufacturing methods. So to me there's not a spitting bit of difference between the various suppliers. In fact about the only thing that could separate them as far as the camshaft itself is concerned is quality control, customer service, and plain old mistakes.

The relationship of intake valve events vs. exhaust valve events is based two or three related things. First, the intake flow is at relatively low pressure (atmospheric without a supercharger), while the exhaust event starts out at relatively high pressure (what's there when the exhaust valve opens, open it sooner and there's more pressure). One way to think of the lift requirement is to think of it in terms of percentage of valve diameter - so intake valves being bigger they need to open farther. Another aspect of intake vs. exhaust timing is what the engine's need for exhaust flow vs. intake flow is. Usually it's around 80-85%. Of course all these things interact, and the cam timing can be used as the final adjustment.

Last thing, and one to always remember. The most important valve timing event is the intake closing. This is what sets the engine's rpm range and torque. The rest can vary a bit without nearly as much effect.

[chevynut]

Last things first. The math of camshaft lobe detail once the duration and lift specs are chosen is well established. It's in a first level kinematics course which many undergraduate engineers take. Computers make achieving it even more convenient.

Well of course I could spend hours weighing parts and calculating forces with equations but it seems like someone, somewhere, should have already done that. ;) Do you know of any calculators that estimate spring rates at various lifts, durations, and RPMs? I don't. Can you refer me to any information on lobe details? I haven't been able to find anything on that. I know Crane has a huge library of cam profiles that show durations at various lifts. If the cam manufacturers have a model, they should be specifying spring rates for their particular profiles, I would think.


Same with the manufacturing methods. So to me there's not a spitting bit of difference between the various suppliers. In fact about the only thing that could separate them as far as the camshaft itself is concerned is quality control, customer service, and plain old mistakes.

I am now set up to degree the cam in, after buying some more tools. :) If the cam doesn't meet published specs, I guess it can go back.

Some suppliers use cast cores of different types. Straub uses something called a "SADI" core which apparently is some sort of cast iron. Sounds to me like someone wasn't happy with what I think is Straub's cam that he had Bullet grind:

http://www.chevelles.com/forums/13-performance/317256-roller-cam-core-materials-cast-sadi.html

It probably doesn't matter with my performance level, but given a choice without a cost penalty I'll take the billet steel core. Apparently customer service is excellent at Howard's...that's some of what I read in other forums...I couldn't find anything negative about them or their products.

It took me 45 minutes on hold to get anyone at COMP to answer the phone. Second time I tried I hung up after 20 minutes. Guys have said if you call on different days you get different recommendations from COMP. I was going to go with the cam COMP recommended at SEMA, but the guy I talked to said he wouldn't us it. One guy said he got an answer in two rings at Howard's Cams, and they responded to my query very quickly. Crane turned me totally off when they said what I wanted couldn't be done even though they did it. Straub seemed tight with his information and I still don't believe my current valvetrain can handle .620" lift to 6000 RPM. Many guys have confirmed that. I feel if I went with a Straub cam I'd be changing my whole valvetrain including lifters eventually. He actually suggested I change lifters too.


One way to think of the lift requirement is to think of it in terms of percentage of valve diameter - so intake valves being bigger they need to open farther.

I guess that goes back to my question...why are intake lifts usually less than exhaust lifts? It would seem that a larger valve would need to open less to get the same flow. Am I misunderstanding something?


Another aspect of intake vs. exhaust timing is what the engine's need for exhaust flow vs. intake flow is. Usually it's around 80-85%.

Are you saying intake or exhaust flow needs to be higher? Seems like exhaust flow should be higher because the gasses are hotter and expand more. My exhaust ports flow less than my intakes, I assume because the valve size is smaller. At 1.88" exhaust diameter they're 83.6% of the intake size. That's just about at 80-85% ;). So because the larger exhaust gas volume and smaller valve size, you need more lift and duration, right? That makes sense, so why is Straub recommending the opposite? Just want to understand where he's coming from.


Last thing, and one to always remember. The most important valve timing event is the intake closing. This is what sets the engine's rpm range and torque. The rest can vary a bit without nearly as much effect.

That's the reason I've calculated intake closing on all these cams and have been looking at the tradeoffs between duration, ICL, and LSA. So it sounds like the intake closing should be prioritized over exhaust opening. And advancing the cam a little increases torque, which is what I'm looking for. The Crane 168761 cam they used to improve the 502 in that mag article had 5 degrees of advance and a 107 ICL and 38 degree ABDC intake closing. Everything else on that cam looks great but I'm concerned about the .610 exhaust lift being too much. They changed to taller lifters.

Thanks for the education.

[Rick_L]

You've taken many of the comments in the last reply in a different context from what I intended.

My first point about the cam lobe is once the duration and the ballpark lift are decided, the exact cam profile is modeled using the principles of kinematics. There haven't been any real advances in cam lobes in maybe 40-50 years - so my point is that a lobe for a cam of X duration with Y lift (and all the other factors) is virtually the same from every manufacturer. The only variations you see are mixing different intake and exhaust profiles and their phasing.

What I'm talking about here is basic stuff and doesn't take into account any dynamics from things like mass and elasticity of the valve train components, at least for a start. Basically a few rules like continuous acceleration curves, plus some things gained by experience as far as the ramps where you can't always follow those rules. I'm not saying you do the kinematics yourself, and I'm saying the cam manufacturers don't do it over and over - they use those 50 year old lobes again and again.

I think you've already experienced the customer service aspect of how the companies differ. Comp is big, their reps don't all have the same expertise, and they aren't trained uniformly either. Straub wants you to think he knows more than the other guys, and he's trying to hook the guy with a bit more money or whatever into spending more and making him a big profit on a single sale. Looks to me like you found him out on the lifters/max lift. Howard? Maybe you were the only call that morning.

Intake flow needs to exceed exhaust flow (on a flow bench that uses the same parameters for both). That DOESN'T mean that the flow conditions in the engine are the same for both. As far as lift/diameter, think about the flow area vs. the entire time the valve is open. The valve flows far more for a single event if you open it further, because it spends less time at low lift and more at high lift.

I don't know where you got your Vizard info on LCA and ICA (which is good stuff), but the book that I have that had that info also spent about 20 pages on related things like flow, lift, lift vs. valve size, exhaust vs. intake flow, etc. I suggest you get a copy. I think the name is "How to Make Horsepower" or something similar.

[55 Rescue Dog]

You can have 1HP 1 ft lb, or 1000 HP with 1000ft lbs on any motor, they all switch sides on a dyno at 5252 RPM. No matter how cool it sounds on paper, building an engine for max power WAY above where you will actually use it, is a total waste of time, and money, and fun. "Torque wins races, Horsepower sells cars"
I have the shift light on my LT-1 set at 5252rpm, as a reference to try and get a better feel for the relationship between RPM and torque. You can have a blast at 1800rpm with torque.

[chevynut]

I've been trying to figure out if I'm over-doing it on lift and whether I'll see any real benefit or just stress my valvetrain more than necessary going from .527 to .600" lift. In doing some reading, I came across this stuff:

"The flow coefficient of a poppet valve peaks approximately when the valve lift is about 25 or 30 percent of the valve diameter. So purely in terms of flow gains, there is no benefit to using more lift than that.

But most racing engines use much more lift than flow conditions require, for kinematic reasons. Using greater valve lift permits a cam profile that will achieve that max flow condition for a greater period of time with a fixed duration. Or in other words, you get to the condition of max flow quicker after the point of intake valve opening, if you employ more valve lift."

My 502 has 2.25" intake valves and using a .600" lift the ratio of diameter to lift is .267 which is in the right range. I've read other sources and they say .25 is the "magic number" which would give me .563" lift is all that's really needed but as stated more lift helps get to the max flow lift point quicker in the cycle. So again the .600 looks like a reasonable number.

I've also looked at a few of the calculations on this page:

http://www.cartechbooks.com/techtips/cylinder-head-math-for-engine-performance/

I don't have flow numbers for my heads with the intake manifold attached, so I can't do many of these calculations. I did find it interesting that the most flow relative to valve open time occurs at about 65% lift. And it looks to me like my heads should support something near 600 HP with no porting. That pretty much lines up with that Straub told me.

As a first pass it looks like my plans for at or close to .600" lift are reasonable given my valve size and port flow numbers. Whatever I do to increase torque at 5000 ft is going to help at sea level too.

I want to be sure to avoid any other issues with this much lift, like valve to piston clearance. However, in looking at the article using the Crane .597/.610 lift cam (230/236 duration) they had .150" intake valve to piston clearance at 5 degrees advance on the cam. My cam should give similar results but I'll check it anyhow.

So the next hurdle is to figure out what I need for valve springs, retainers, or other parts to get me a reliable valvetrain that won't float the valves at under 6000 RPM. I haven't found any good sources for doing these calculations. Both Straub and Howard's Cams said my current springs should work, but I'm skeptical based on reading about valve float issues on other forums.

If I get new springs I'll probably have to get new retainers and locks as well. I may go with the lightweight tool steel retainers for a few more bucks to keep the spring forces down as low as I can and still control the valves. They're a lot cheaper than titanium and I read one post on a forum that said a guy went to titanium retainers on his 502 and it greatly improved his valve float problem. I don't know if my new COMP rockers are heavier or lighter than the stock ones. On the other hand, if the lighter retainers work on my existing springs an get me reliably to the 5800 RPM limit specified by GM maybe I'll just set my rev limiter there. ;)

Part of the reason I'm doing this stuff is just to learn more about cams and valvetrains an what makes them work well. I'm not trying to get every last HP or ft-lb of torque I can get, just trying to optimize things for my application as well as is reasonable without spending a ton of money.

I have been wondering why the stock lifters "aren't happy" with more than 150 lbs of seat pressure (I'll call it pressure since everyone else does ;)). I'm not very versed on how a hydraulic lifter works and what makes it collapse or malfunction, so I guess I'll have to study that too. :) In the Crane cam swap article they used 200 lb on the seat and 500 lb at .600" lift, which I feel is excessive based on my other readings.

I got my valve micrometer today so I'll take a look at installed heights and see if my existing springs can be made to work.

[chevynut]

Here's some stuff I found on valve spring pressures:

"Hydraulic Roller Cams Hydraulic roller (HR) cams require higher pressures to control the inertia of the heavier roller lifters and the faster acceleration of valve train components allowed by the use of the roller follower. Pure street small blocks should have 260-300lbs open pressure. For performance use, aim for 300-350lbs open. Racing small blocks that regularly see 6,000+rpm need over 400lbs open pressure. At these pressures, premium valve train components including a “billet” type cam are required. Even with these components, there will be reduced service life and the consequent need for more frequent parts inspection and replacement. Big blocks need closer to 300lbs open pressure for street driving and 350-375lbs is preferred for performance use. A racing big block needs 450lbs. As with small blocks, premium components including lifters are needed at higher pressures and rpm. As with solid lifter cams, seat pressures should be in the range of 105-125lbs for small blocks and 115-130lbs for big blocks for performance street cars. Blower cars and race cars will need higher seat pressures."

http://www.crankshaftcoalition.com/wiki/Valve_spring_tech

"Hydraulic roller cams require higher seat pressures to control the heavier roller tappets and the more aggressive opening and closing rates available to roller cam profiles.



Small block applications: 120-145# seat pressure
Big block applications: 130-165# seat pressure


Hydraulic roller cams require higher open pressures to control the high vertical opening inertia of the heavier roller lifters.

Small block applications need at least 260# for general performance applications up to 4000 RPM (http://rover.ebay.com/rover/13/0/19/DealFrame/DealFrame.cmp?bm=432&BEFID=96477&acode=420&code=420&aon=&crawler_id=527423&dealId=VB9uifRRSllmGer6YXD8Fg%3D%3D&searchID=&url=http%3A%2F%2Fwww.corvettemods.com%2FUniversal-Corvette-1968-2014-Autometer-2-58-inch-Pedestal-Tachometer-0-4000-RPM_p_13238.html&DealName=Universal%20Corvette%201968-2014%2B%20Autometer%202-5%2F8%20inch%20Pedestal%20Tachometer%200-4000%20RPM&MerchantID=527423&HasLink=yes&category=0&AR=-1&NG=1&GR=1&ND=1&PN=1&RR=-1&ST=&MN=msnFeed&FPT=SDCF&NDS=1&NMS=1&NDP=1&MRS=&PD=0&brnId=2455&lnkId=8070676&Issdt=160509051318&IsFtr=0&IsSmart=0&dlprc=151.99&SKU=13238).
Moderate performance small block applications like 300-360# open spring pressure.
Serious small block applications can tolerate 400-425#* open pressures and still expect reasonable valve train life when top quality springs, pushrods, and lubricants (http://www.ebay.com/sch/i.html?_nkw=lubricants) are used.
Big Block applications need at least 280# for general performance applications up to 4000 RPM.
Moderate performance big block applications like 325-375# open spring pressure.
Serious big block performance applications can tolerate 450#* open pressure and still expect reasonable valve train life when top quality springs, pushrods, and lubricants are used.
Note: Open pressures in excess of 360# require the use of roller tappet bodies made of billet steel. Crane hydraulic roller and solid roller tappets are made from heat treated steel billet to withstand the stresses of high-performance use. Most stock hydraulic roller tappet bodies are made of cast iron and cannot tolerate high spring loads.

[Rick_L]

High spring pressures are no doubt going to control the valve train better. The question is how much is too much.

When you get too much spring, to me the biggest risk is problems with the axle, roller needles, and roller. They wear. The consequences of that wear can be catastrophic. Thing is, weak springs are just as hard on these items, because the valve/lifter float results in impact forces that can be severe. In my racing days, we had some big wear problem with the lifters after going to a spring that had 350 lb on the seat (previous was about 225-250).

If you look at some of the choices offered on Morel lifters, they offer "bushing lifters" which means they have a bronze bushing for a bearing in the roller rather than needles. This also allows a bigger axle. Also, they have lifters that are bigger diameter than stock, which means that the roller/bearing/axle package can be bigger.

Isky also has "bushing lifters", though I'm not sure whether they offer that in a hydraulic lifter.

If you remember from a few posts back in the thread, I mentioned that a friend broke a solid lifter in a BBC, and he's now considering how to proceed, with similar choices to yours. In that one, a roller broke into 3 pieces, and scattered the needles throughout the engine. I don't know whether the axle was worn or not. He got lucky in that the damage was restricted to ruining the cam, the damaged lifter itself, and possibly the lifter bore. So the engine is very repairable. He had K-Motion 1000 springs which are about 225 pounds on the seat new and probably about 190-200 pounds after some miles.

[chevynut]

Just out of curiosity I was looking at Morel lifters. For some reason that have BBC lifters for 87 and older blocks (#5374) that have only a .700" roller instead of the standard .750" roller. The body diameter is the same. Why would you need a different roller for the older blocks? The lift profile would obviously be affected.

One thing that bothers me is their inconsistent specs. One place says the wheel is .750" and the other says .700" for the lifters I'd need. The picture on the Morel-lifters.com website is wrong. Makes one question their attention to detail if they can't even get their specs right.

http://morel-lifters.com/chevy-bb-hydraulic-roller-lifters-5475/
http://johncalliesinc.com/product.php?ProductNo=5475
http://johncalliesinc.com/morel_products.php

They don't specify the weight of the lifters, nor whether they use bushings or needles.

Looks like the lifters I'd need (#5475) are $658 a set and those are the "cheap" ones. Really don't want to get to that point. :(

[NickP]

One thing that bothers me is their inconsistent specs. One place says the wheel is .750" and the other says .700" for the lifters I'd need. The picture on the Morel-lifters.com website is wrong. Makes one question their attention to detail if they can't even get their specs right.

http://morel-lifters.com/chevy-bb-hydraulic-roller-lifters-5475/
http://johncalliesinc.com/product.php?ProductNo=5475
http://johncalliesinc.com/morel_products.php

They don't specify the weight of the lifters, nor whether they use bushings or needles.

Looks like the lifters I'd need (#5475) are $658 a set and those are the "cheap" ones. Really don't want to get to that point. :(

Regarding the size difference (.700 vs .750), did you call to determine what size they are? It may be a simple typo done by the webmaster.

[chevynut]

I just checked my installed heights and ran into some interesting stuff.

#1 intake 2.040
#3 intake 2.038
#5 intake 2.039
#7 intake 2.044

#1 exhaust 2.044 (outlier)
#3 exhaust 2.058
#5 exhaust 2.059
#7 exhaust 2.057

#2 intake 2.030
#4 intake 2.027
#6 intake 2.030
#8 intake 2.027

#2 exhaust 2.052
#4 exhaust 2.064 (outlier)
#6 exhaust 2.050
#8 exhaust 2.051

I tapped the valve tip with the end of a screwdriver handle to ensure the locks were seated when measuring with the micrometer. I noticed a while ago that #1 exhaust retainer and lock didn't "seat" correctly and the retainer rocks when the lock is in place. It measures shorter than the other cylinders on the same head by about .015", and I even measured it twice after re-installing the parts the second time. I'm not sure what's wrong but I see nothing visually. I put the #3 locks on it and it went to 2.054", then I put the #3 locks and retainer on and it went to 2.057". So something seems to be wrong with the retainer and lock on #1 exhaust valve....I'll have to look more closely.:confused:

The other thing I noticed is the intake heights on one head are about .012" different than on the other head, on average. Also, the #4 exhaust height seems a little out of whack, by about .013" from the rest on that head. Not sure why that's the case either.

Anyhow, the GM specified installed height is 1.940" for all springs and these all measure much higher than that by about .087-.104" on the intake side and .110-.124" on the exhaust side.

As I mentioned before, all intake springs have a .062" shim with #5 and #7 having an additional .0175" shim. Those two springs had the lowest pressure at 2.00" so that's probably why they did it. The exhaust springs all had a .062" shim plus a .032" shim for a total of .094".

With the .062" shims the average installed height of the intake springs is still 1.973" which is still .033" over spec. On the exhaust side they averaged about 2.055" (excluding #1) and with the shims the installed height is 1.961", still .021" over the 1.940" spec.

I don't know how critical one needs to be with this, but a .030" discrepancy changes the seat pressure on these springs by around 11 pounds....that seems very significant to me. Perhaps that helps explain why some of these engines float the valves before redline. Some have speculated that GM did this on purpose. ;)

So to me the "installed height" specs on valve springs are BS. I don't understand why they don't just give you the pressure at some fixed compression length along with the rate and let you figure out what you need from there.

[Rick_L]

The variation in available spring height that you measured is quite typical, and the fact that it's more than spec is also typical. You just don't see precision any closer than that. The other half of this is if you had a set of cast iron factory heads which have had a valve job or two - there would be even more variation.

The space you are measuring is affected by the head, the valve, the keepers, and the retainers - and they all have tolerances.

Your job is to fix that with shims, and also to fix any weak springs with shims. Or maybe rank them and use the weak ones on the exhaust.


I don't understand why they don't just give you the pressure at some fixed compression length along with the rate and let you figure out what you need from there.

That's exactly what you need to do and what happens in good engine shops every day.

The installed height thing is a reference. It does have some bearing as to coil bind height and whether you can even use the spring at all. For instance, if you were picking a spring and found one that met your expectations except that it had a 2.25" installed height, you'd know right away not to consider it. Or for that matter one that had a 1.75" installed height.

[55 Rescue Dog]

Using what you already have is free horsepower. Going bigger on everything is going to have it's own issues, plus lots of money.
Building for big power at the track is when you can use the higher power band, but on the street, unless you are on the rev limiter all the time, the big cam, springs, and money, is using way more wasted power than you gain every mile of real world driving. The engine just plain doesn't have to work as hard, when it doesn't have to turn the big cam, and compress the heavy springs just to idle at stop light. Being first on a green light is where it's at.

[chevynut]

Decided to send Mike Jones a cam recommendation request since he did Chad's cam. Here's what I got back. He's in "left field" compared to everyone else as far as LSA and duration is the same on the intake side as my current cam, and shorter on the exhaust. Hmmmm. I really don't think that's much of a step from what I have.

Here's what I recommend.
BBCHR, HR70340-70335-108
272/280 @.006"
224/226 @.050"
.340"/.335" Lobe Lift
.584"/.576" Valve Lift w/1.72 rockers
108 LSA
Price: $441.64

[Bitchin'57]

Decided to send Mike Jones a cam recommendation request since he did Chad's cam. Here's what I got back. He's in "left field" compared to everyone else as far as LSA and duration is the same on the intake side as my current cam, and shorter on the exhaust. Hmmmm. I really don't think that's much of a step from what I have.

Here's what I recommend.
BBCHR, HR70340-70335-108
272/280 @.006"
224/226 @.050"
.340"/.335" Lobe Lift
.584"/.576" Valve Lift w/1.72 rockers
108 LSA
Price: $441.64
There you go, high lift with short duration.

[Rick_L]

As bitchin' said, you got the short duration/high lift you've been lusting for. I'm not sure that the 108 degree LSA is what you want.

BUT, as I keep saying, you're splitting hairs here and you won't see a difference between them all.

[Bitchin'57]

As bitchin' said, you got the short duration/high lift you've been lusting for. I'm not sure that the 108 degree LSA is what you want.

BUT, as I keep saying, you're splitting hairs here and you won't see a difference between them all.
The Jones cam isn't THAT much different from the Lunati cam I had suggested, with respect to lift and duration. I agree with Rick, don't slip into paralysis by analysis. When in doubt, go with the shorter duration cam. It won't sound as racy aas the long duration cam, but it will perform much better on the street.

[Bitchin'57]

As bitchin' said, you got the short duration/high lift you've been lusting for. I'm not sure that the 108 degree LSA is what you want.


I read of back to back dyno tests, comparing cams that were identical in terms of lift and duration, only difference being their LSA. One cam had 112 LSA, and the other had 107 LSA. The cam with the lower LSA made better low end torque, but not by a bunch.

[chevynut]

Thanks for all the feedback Rick. ;)

When I looked at the installed height with the shims I got a standard deviation of only .007" and the average was 1.964" (spec is 1.940"). Coincidentally the high and low were both on #1 cylinder with the intake at 1.978" and the exhaust at 1.950" (bad lock).

I took another look at the #1 exhaust valve locks and there is definitely something wrong with one half of the lock. I swapped one half at a time to #3 exhaust valve and the retainer rocks slightly when I put the bad half on it. It's either the wrong part or it's damaged. It seems to have a slightly smaller radius than the other half. All the other locks hold the retainer tightly to the valves.

I went through the spring pressure calculations using the spring measurements I got before and I get an AVERAGE seat pressure including shims of only 131 pounds (spec is 140). The high is 136 (#4 intake) and the low is 124 (#4 exhaust). At .600" lift I get an average of 342 with a high of 351 (#1 intake) and a low of 336 (#5 exhaust). That's with the stock shim placement.

These springs bind at 1.200" so I have quite a bit of room to shim. Good idea using the weaker springs on the exhaust side. The highest spring rate I calculated was 372 lb/in (coincidentally on #1 intake that had one of the LOWEST seat pressures). Using that spring I'd need to shim it another .062" to get to 150 pounds on the seat (max recommended for these lifters) . Then at .600" lift I'd be at 373 pounds. I'd still have .116" before coil bind.

Based on what I'm seeing it's not surprising to me that guys are getting valve float with these engines out of the crate. I think I need somewhere around 375 pounds at max lift for this to work, or slightly less with lighter retainers. I wonder how much reducing retainer weight by about 1/3 (as advertised) would help. The 1.5" tool steel retainers are about 20 grams. I don't know what mine weigh.

Just to be thorough I measured the retainer to valve seal height and got .867" so no problem there. :)

[chevynut]

Every other cam supplier besides Jones said to use a 112 LSA so I think that's what I should be shooting for. Jones didn't specify the ICL so I can't calculate the ICA or advance. Since it's such a short duration maybe it's not necessary but it would be interesting to compare.

I'm not too worried about over-analyzing anything because I'm learning a lot. It'll get done when it gets done, and I feel I'm making progress with everything else I have going on. I want to be sure I optimize everything I can and don't overdo or overlook anything that might cause a problem. In looking at all the factors I keep uncovering new things, like rocker performance. For example, I hadn't thought about the stock rockers possibly not having a long enough slot to work with the higher lift, but I have that covered. ;)

I did some reading of a very interesting Big Block Chevy build book by Vizard that's fairly new, published in 2015. His work has apparently been focused on BBCs, which I didn't know.

http://www.amazon.com/Build-Max-Performance-Blocks-Budget-Design/dp/1934709387#reader_1934709387

One chapter is about "Valvetrain Optimization". He says a BBC needs a LOT of lift due to being "grossly" under-valved no matter what heads you put on it. He also says that the priorities for a performance BBC are to get the heads to flow as much as possible, get the intake to flow as much as possible, and get as much lift as possible. He says it's important to lift the valve as fast and as high as possible for a BBC due to it being so under-valved.

In that same book I read some evaluations of different rockers that he did, looking at actual lift ratios. He says a rocker's "advertised ratio" can differ a lot from it's actual "working" ratio. He tested many rockers using what he called a "moderately hot street hydraulic roller cam of 230 duration" which he says is what he recommends for a strong, streetable BBC. All evaluation was done with a .352" lobe.

The results were very interesting. He says the stock GM "1.7 ratio" stamped steel rocker only has an initial ratio of 1.01:1 and a TDC ratio of 1.11:1 with an overall ratio of 1.679:1. In contrast, the Comp Magnum roller tipped rocker has an initial ratio of 1.65:1, a TDC ratio of 1.685:1, and an overall ratio of 1.79:1!!

For the COMP Magnum roller-tipped rockers he says "Comp Cam's cast stainless steel roller-tipped rocker, rated at 1.72:1, is my best bang for the buck". The reason why is that they actually deliver a 1.79:1 ratio in use.

He goes on to say the stamped steel and COMP cast stainless Magnum rockers are intended to be used with springs that have a max pressure of 375 pounds at full lift. I just looked in the COMP catalog and they say they're intended for applications with less than 350 pounds of open pressure which I somehow missed. :eek:

So now I have to factor in that info into my cam and valvetrain decisions so I don't get too much lift. I could get .562" lift with my stock cam. :)

Another thing...he's a big proponent of beehive springs.

[NickP]

Laszlo, I guess I'm confused as to the final intent of your Nomad. What was it again? 90% drive and enjoy with 10% on a track of sorts? I mean no disrespect by this comment but I just don't see the need for all of this unless the plan has reversed. Again, I'm not being negative in any form.

[chevynut]

Here's some more from Vizard on the COMP Magnum rockers and other stuff:

"The Magnum style rocker from Comp Cams gets my "best buy" recommendation based on what it costs versus what it delivers in performance and reliability. Although advertised as 1.72 the ratio delivered is considerably more. With the short test cam the off-the-seat ratio is so much higher that the valve, at TDC, was open 52% farther than the stock factory rocker. These rockers are a great deal, especially for short-cammed, street driven big blocks."

"Some application specific recommendations for optimizing their use are in order. As mentioned in Chapter 9, Camshaft and Valvetrain Events, the exhaust valve is more sensitive to duration than it is to off-the-seat acceleration. This means that if both intake and exhaust are equipped with Comp's Magnum rockers, for a dual pattern cam the exhaust lobe of the cam needs to be no more, but preferably as much as .020 less lift than the intake along with about 4 to 8 degrees more duration. If you're doing a low-buck build with a stock stroke these rockers work well with Comp's Thumpr cams for engines from 427 to 480 ci. These cams are ground on a 107 LSA, which is close to perfect for most engines in the displacement range just mentioned. That's particularly so when using factory heads with minimal modifications."

"Opt for a single pattern cam if you're looking for the best deal in idle quality and mileage as well as strong top-end output. "

He goes on to recommend COS-cam for a cam source. http://www.twperformanceparts.com/index.php?route=product/category&path=982

[chevynut]

Laszlo, I guess I'm confused as to the final intent of your Nomad. What was it again? 90% drive and enjoy with 10% on a track of sorts? I mean no disrespect by this comment but I just don't see the need for all of this unless the plan has reversed. Again, I'm not being negative in any form.

No Nick, probably no track (drag strip) time, 100% street and maybe a little fun autocross someday if I get the urge :). I just want a strong, reliable engine that performs well at my altitude. I think some optimization is reasonable. Why is that so hard for some of you to understand?:) :) (no disrespect intended) I don't want valves crashing into pistons, springs breaking, poor idle, bad throttle response or crappy low-to-midrange performance. I also think that 6000 RPM without any hiccups is a reasonable goal but maybe I need to re-think that. Who knows, I may never get over 5500. ;)

I put the roller tipped rockers in the plan because I thought they were a reasonable low-cost upgrade from stock at $137. They have benefits (higher ratio) and limitations (350 lb spring pressures) that I didn't know about, and that factors into my other plans.

[NickP]

No Nick, probably no track (drag strip) time, 100% street and maybe a little fun autocross someday if I get the urge :). I just want a strong, reliable engine that performs well at my altitude. I think some optimization is reasonable. Why is that so hard for some of you to understand?:) :) (no disrespect intended) I don't want valves crashing into pistons, springs breaking, poor idle, bad throttle response or crappy low-to-midrange performance. I also think that 6000 RPM without any hiccups is a reasonable goal but maybe I need to re-think that. Who knows, I may never get over 5500. ;)

I put the roller tipped rockers in the plan because I thought they were a reasonable low-cost upgrade from stock at $137. They have benefits (higher ratio) and limitations (350 lb spring pressures) that I didn't know about, and that factors into my other plans.


I'm fully on board with Blue Printing for the sake of a better term, I just don't see the need for the race type items specific to your presently stated design intent. Reliability being at the top of your list seems to negate the specialized or race type parts. I just wonder that were you to be in some remote location how quickly one can acquire some bumble bee hive springs and roller rockers and special lifters with a 2 week lead time. I'm not judging just trying to see the practicality of it versus stock parts that may make a few HP less but are more available at a local parts store should the need arise.

[55 Rescue Dog]

Why not just put on the Comp Cam Magnum XD 1.73 full roller rockers, and see what happens? All you would need to do is maybe use a different valve cover. Simple solution that will make a difference.

[chevynut]

I'm fully on board with Blue Printing for the sake of a better term, I just don't see the need for the race type items specific to your presently stated design intent. Reliability being at the top of your list seems to negate the specialized or race type parts. I just wonder that were you to be in some remote location how quickly one can acquire some bumble bee hive springs and roller rockers and special lifters with a 2 week lead time. I'm not judging just trying to see the practicality of it versus stock parts that may make a few HP less but are more available at a local parts store should the need arise.

Nick, I don't know where you're coming up with the idea that I'm looking for "race type" parts. LS engines all have beehive springs in them. They might help solve the problem I have.

Let me explain it to you.....this engine had a couple of problems when I bought it, as all of them do. First off is the low-tension oil rings which is a known issue and causes some of these engines to burn oil. I didn't want that to happen so my plan has ALWAYS been to replace the oil rings with standard tension ones. In the process I just installed a complete set of Total Seal file-fit rings. Total Seal recommended that I have the block honed with a torque plate to make the cylinders round with the heads on, so I did that. It should help cylinder sealing for the street, not just for max HP. And it should help control oil better as well. I almost didn't go with file-fit rings but the shop that I had do the honing recommended the file-fit rings to me. They cost the same, just needed a bit more work to get them gapped. And it was kinda fun anyhow ;).

Next is the cam. I've said for years that I may bump up the cam a bit to get a little more power out of the engine. Several people have said these engines have a "small" cam and there's a lot of potential power to be had pretty easily. I have been researching this upgrade and recently found out that some of these engines won't rev past around 6600-6800 RPM because of valve float. A bigger cam just makes that worse, and I think I want 6000 reliable RPM which is nowhere near unreasonable, imo.

So let me ask you this...would you be happy with a 502 inch BBC that makes 400 horsepower at the flywheel and maybe 320 at the wheels? That's what happens at 5000 feet elevation...you lose 20% HP due to the thin air and around 20% more through the drivetrain. That's pretty wimpy, imo, for such a big engine. So what can I do about it?

First, I want to try to address the "small cam" and increase the HP/torque and focus on optimizing it at 5000 ft elevation. Per several cam suppliers, I need a high lift, short duration cam. It also needs to have an early intake closing event because of my relatively low 9.6:1 compression ratio and the thin air which will kill my cylinder pressure. So I'm looking at something that will give me .600" lift at the valve and early ICA.

I learned that the "dogbone" lifter retainers on this engine can be an issue with a bigger cam. If the lifter drops too far below the retainer, it can actually lift the retainer and the engine gets trashed. I have done some measuring and when the lifter is on the base circle of the stock cam, the top of the lifter sits about .023-.026" above the retainer. To get higher lift with these cams they don't increase the size of the lobe, they decrease the size of the base circle. Right now the .320" exhaust lobe is almost as tall as the journal. As the base circle decreases, the top of the lifter drops down into the retainer.

One solution to the problem is new lifters...at $600-900. I don't want to do that. Luckily I just found out that my new roller-tipped rockers have a much higher ratio than advertised, 1.79 instead of 1.72. It looks like the advertised 1.72 is the AVERAGE of the ratios off the base circle and at max lift. The stock rockers don't perform nearly as well so I gain lift everywhere. This does a couple of things...the COMP Magnum rochers give me a roller tip for better wear and they allow me to use a smaller lobe lift to get to .600" valve lift. So I've reset my cam selection to look at that as well.

Next, there's the issue of valve float. This is an inherent problem in the BBC heavy valvetrain design. My intake valves are a huge 2.25" and they're fairly long. They have 11/32" stems that are reduced in size near the bottom so that helps. The exhaust valves are 1.88" so they're not as much of a problem. I've read some speculate that the real issue is the roller lifters as they are pretty heavy. As I go to higher valve lift, it becomes even more critical for me to control the valves. The reduced lobe lift helps keep the lifter in control so these rockers really help.

Looking at my current dual springs I see some opportunity to increase the pressures by using more shims. It seems like perhaps GM under-shims them for some reason. However, I've also learned that the lifters don't like anything more than about 150 pounds on the seat or they start to make noise. I'm not sure why that's an issue, but 150 pounds seat pressure is pretty high from what I've seen and the GM spec for these is 140.

My stiffest 8 springs average about 360 lb/in. So if I'm at 150 on the seat, the max I can get with .600" lift is 366 pounds. That may work to prevent valve float to 6000 RPM but I'm not sure. My engine was set up with an average of 316 pounds over the nose of the cam at .527" intake lift so that was pretty low. It may be the reason others have a valve float issue. Some of what I've read says I may need to be closer to 400 with the stock valvetrain, but a couple of the cam suppliers including Straub and Howard's cams, but I gave them the GM specs for the springs which are 140 seat and 368 lb/in (360 lb at .600").

The other issue I just found out about is my new rockers (and the stock ones) aren't rated for more than 350 pounds pressure (per COMP) or 375 pounds (per Vizard). Since this isn't going to be a race engine, I think 375 might be just fine...COMP may be conservative.

So what's the solution to this dilemma? I'm trying to get more lift with an aggressive cam and the current springs are marginal. It might work with the stock springs shimmed up, but nobody can tell me for certain and I don't want to mess with it after installation.

There are some possibilities:

1. Shim my springs - I already outlined what I could do. It may work fine now with the reduced lift required with the new rockers. They would be at the limit of my rockers.

2 - New dual springs - I would need to get new springs if I wanted higher over-the-nose pressure and leave the seat pressure at 150, but as I said I'm not sure my rockers would like that. Springs, retainers, and locks would run around $250.

2. Lighter retainers - They make titanium retainers that cost around $350 a set. They also make tool steel retainers that are just a smidge heavier and cost a lot less. The problem is I'm not sure I can find any to fit my current stock springs correctly. My current retainers actually snap lightly into the spring and nothing I've found will fit that well. I may only need to do this on the intake valves, but I'm not sure since some say the lifters are heavy. I would use my stock springs. Tool steel retainers run around $150 and new locks (they take 10 degree locks) would be another $23 for a total around $173.

2. Beehive springs - These springs allow the engine to run with a lower seat and over the nose pressure because they themselves are lighter at the top, and also use a much smaller retainer which is lighter. I found a set from PAC Springs sold through Trick Flow that are only $160 for a set of 16. Retainers are $60 and new locks are $23 for a total of $243. I might get away with only using these on the intake valves but don't know if it makes sense. My only concern with the beehive springs is there's no backup if one breaks, and I've read about some breaking. I read about one guy who broke 3 COMP beehive springs but I don't remember the application...he might have been really stressing them.

So this isn't about wanting to get exotic, it's about trying to make everything work together to get some more high altitude power and solve the valve float issue which gets worse with the new higher lift cam.

Hope that helps you understand where I'm coming from. ;)

BTW, I tried to verify the rocker ratio today by installing a pair of valves with my checking springs and installing the head and cam, but my hydraulic lifters collapse so I can't get a lift measurement. :( So I guess I have to trust Vizard.

[chevynut]

If you Google "broken beehive spring" you'll find a lot of this:

http://ls1tech.com/forums/lt1-lt4-modifications/1600944-beehive-springs-strikes-again-edit-now-called-engine-rebuilt-2013-a.html

https://www.google.com/search?q=broken+beehive+springs&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjMt--V4NXMAhXJOyYKHRaZAeoQsAQIPQ&biw=1280&bih=869

I'm feeling that my current springs shimmed up some and with a lighter retainer might be the way to go. Hope I can find something that will work.

[Rick_L]

The "race parts" deal needs context. Many "race parts" are much more reliable than stock parts.

It's not what you have, it's what you have relative to the way you will use it, and what else you have. Everything needs to match up.

That's why you need a lifter upgrade at a certain point, that's why full roller rockers are a good thing, why dual springs and light but strong retainers are a good thing, etc.

But thing is, will the winch in your trailer over rev the engine?

[markm]

I have heard it said many times people are happier with a cam that is a little small than one that is too big. No place is this more relevant than a show car. I am happy with oem fit and finish for the most part , you obviously are not, however I run the shit out of things. If it was my car I would worried about the Dana 44 and figuring how to change to a 60 like the Viper race guys. That is why the following is such good advice


It's not what you have, it's what you have relative to the way you will use it, and what else you have. Everything needs to match up.

[chevynut]

Rick, I don't own a car trailer. ;)

If anyone is interested in some technical engineering stuff on cam design and performance, I found this very interesting site:

http://www.tildentechnologies.com/Cams/CamPerformance.html

[chevynut]

It's not what you have, it's what you have relative to the way you will use it, and what else you have. Everything needs to match up.

And that's exactly what I'm trying to accomplish....the best match of parts that will do what I want without going overboard.

As for the Dana 44, it's a Dana 44 HD. It's reportedly as strong as a GM 12-bolt which many say is about the same strength as a Ford 9". I don't need a heavy boat anchor in the rear for what I plan to do with this car. I won't be dropping the clutch at 5000 RPM. I already upgraded the driveshaft to a 3.5" MMC aluminum one with 1350 u-joints and a new 1350 Spicer rear yoke. The halfshafts are getting solid 1350 Spicer u-joints as well. I've heard of Vipers running 10 seconds in the quarter with the same Dana 44HD. Mine isn't a drag car.

This one ran in the 7's with the IRS, probably modified to some extent.

http://www.dragzine.com/news/99-dodge-viper-runs-7-56-on-drag-radials-with-irs/

This one got into the 6's:

http://www.dragzine.com/news/sal-patels-viper-first-in-the-sixes-sets-new-irs-world-record/

"Patel’s rear suspension still uses the factory Independent Rear Suspension from Chrysler, which makes the numbers it produces all the more impressive. Almost a year ago Sal busted out a 7.11-second pass in the quarter mile to claim the overall IRS record, but he wanted to be the first to break the six-second barrier with such a combination."

Apparently Mark knows as much about a Dana 44HD IRS as he knows about camshafts. :D

[Rick_L]

And you know as much about a Dana 60 as you claim to know about car trailers.

[chevynut]

I installed a Dana 60 in the gasser frame we built last year and it was a huge piece of iron. It's not necessary to put anything like that in a street car, or even most drag cars, IMO. ;)

Besides, this thread is about my Ramjet 502 re-assembly, not differentials. Mark can't ever seem to stay on topic.

[chevynut]

I did some checking of my stock 502 cam with the new rockers today and got to use all my new cam degreeing tools ;). Here's my results, which I checked several times.

Intake
39* BTDC .006"
19* BTDC .050"
TDC .124"
Max lift .531" (factory spec is .527")
45* ABDC .050"
76* ABDC .006"
Advertised duration 295*
.050" duration 244* (factory spec is 224*)
Rocker ratio at max lift 1.713


Exhaust
85 BBDC .006"
64 BBDC .050"
BDC .392"
max lift .556" (factory spec is .544")
11 ATDC .050"
44 ATDC .006"
Advertized duration 310
.050" duration 255
Rocker ratio at max lift 1.738

So this sort of confirms what Vizard has published in his book about the COMP rockers. As the lift increases, the effective rocker ratio increases. The stock rockers are supposed to be 1.7, but I think I'll put them on and see what they do.

The crazy thing to me is the increased duration at .050" with the COMP rockers. The GM cam spec is 224/234 and I got 244/255. I don't know where I could have made a mistake and I rotated the engine several times from .050" to .050" on each side of the lobe. How could this be so far off? There's 20 degrees more duration at .050". I wonder if they spec the duration based on the factory rockers rather than the lobe height. Vizard says the factory rockers are only 1.11 at TDC (intake) and the COMP rocker are 1.685 at the same place.

The advertised duration is about what I've seen published by others (it's not spec'd by GM) at 294/304. I got 295 and 310 at .006" and I understand it's hard to get accurate, repeatable measurements at that low lift.

If these results are correct, the COMP Magnum rockers make the cam quite a bit bigger than advertised.

[chevynut]

Ah, it just occurred to me that duration is measured by LOBE lift, not valve lift. Now it makes sense. I guess I'll have to re-do it and see if I can figure out what the impact is on duration with the new rockers.

[markm]

I installed a Dana 60 in the gasser frame we built last year and it was a huge piece of iron. It's not necessary to put anything like that in a street car, or even most drag cars, IMO. ;)

Besides, this thread is about my Ramjet 502 re-assembly, not differentials. Mark can't ever seem to stay on topic.

Says the guy who has Never been involved in competitive drag racing, a Dana 60 is the only rear axle that will take 700hp in stock form. A 9 inch or 12 Bolt will not, ask me how I know, been there done that. A 60 takes less HP to spin than a Ford, they are cheap to build, lots of reasons to use one, well maybe not in a show car.

[55 Rescue Dog]

Who can't be impressed with $137 really cool roller tipped rockers?

[chevynut]

I just got back from Casper WY last night and decided to re-check my results. When I installed my COMP rockers I didn't lube the pivot balls and I noticed I got a little "chatter" from them. So today I lubed them and re-measured the valve lift on intake and exhaust valves.

I got .537" intake and .563" exhaust, which is a little higher than I had before. I think the rocker was sticking a little and not sliding like it's supposed to. This is .010" more on the intake and .019" more on the exhaust than GM specifies for this cam.

So my new ratios are 1.732:1 at .537" lift and 1.759:1 at .563" lift. Interestingly if I extrapolate this out to .600" lift I get 1.794:1 which is close to the 1.79:1 that Vizard reported from his testing. ;) I can't think of a way to simulate a .335" lobe height which would give me a .600" valve lift at a 1.79 ratio.

I also measured my cam and found that the exhaust lobe is only .004" lower than the cam journal. So clearly any lift gain would have to be a result of a smaller base circle.

I ordered Vizard's book and I'm going to read what he says about cam selection before I go any further. Seems like Mike Jones and Vizard are on the same page.

[chevynut]

Who can't be impressed with $137 really cool roller tipped rockers?

David Vizard sure is, and he says they're the "best bang for the buck". I think he knows a helluva lot more than you do about BBC engines, and probably everything else.

The COMP Magnum rockers are built out of 8620 chrome moly and eliminate tip friction. They give a lot better ratio than the stamped stock rockers BBCs come with throughout the operating range. I know a full roller is better but I want to keep my original valve covers as I've explained before but you don't seem to listen. So WTF is your problem with them?

[chevynut]

Says the guy who has Never been involved in competitive drag racing, a Dana 60 is the only rear axle that will take 700hp in stock form. A 9 inch or 12 Bolt will not, ask me how I know, been there done that. A 60 takes less HP to spin than a Ford, they are cheap to build, lots of reasons to use one, well maybe not in a show car.

So do you really think I give a shit about that? I don't, so STFU about differentials in this thread...it's about my Ramjet 502 assembly, in case you can't read (which you seem to have a problem doing). The way you pick cams (just add more duration) makes me suspicious about everything you claim. I wouldn't put a huge chunk of iron like that boat anchor in any car. There's lots of "show cars" that could put your POS to shame on the racetrack. One more off-topic post from you and it's getting deleted from this thread...I don't give a shit what you have to say about it. That's a warning, so stay on-topic.

If you want to discuss differentials, start your own thread. You guys are two peas in a pod.

[55 Rescue Dog]

Why not just put on the Comp Cam Magnum XD 1.73 full roller rockers, and see what happens? All you would need to do is maybe use a different valve cover. Simple solution that will make a difference.
Most of the friction from stamped steel rockers is in the pivot ball, as you noted. Hope you used lots assembly lube on every moving part, after rotating the assembly so many times without oil flow! The tip doesn't move that much. Good steel FULL roller rockers is a good way to go on a strong street engine. With stamped steel rockers, it will end up poking a pushrod through the valve cover. Had it happen twice.

[chevynut]

Most of the friction from stamped steel rockers is in the pivot ball. The tip doesn't move that much. Good steel FULL roller rockers is a good way to go on a strong street engine. With stamped steel rockers, will end up poking a pushrod through the valve cover. Had it happen twice.

There you go again about what's "best". I know most of the friction is in the steel ball, but there have been millions of engines built with them and they work just fine. There are thousands of high performance street engines running around that don't use full roller rockers.

The roller tip on the COMP Magnums allows the rocker to roll across the tip of the valve and imparts no side loads to it. And these rockers aren't stamped steel, they're cast chrome moly. They're a great upgrade from the stock stamped rockers at a bargain price. You might want to research things before you post.

Do you have a reading problem RD? I know what's "best" but full rollers aren't necessary for my car and the way I plan to drive it along with my desire to use the stock valve covers that I've explained several times. I will probably put 2-3K miles on it a year like I do my Porsche.

Are you planning to put all the "best" parts in your car?

[Rick_L]

I know a full roller is better

Then why don't you buy some? Might be a better buy than a camshaft and/or lifters. Just sayin'.

[chevynut]

I just installed the stock stamped rockers and repeated the tests.

Both sets of rockers hit .050" lift at about the same crank angle. After that, the COMP rocker has gradually more lift until the peak, and both intake and exhaust have .024" MORE lift at the peak with the COMP rockers than the stock ones. Vizard is right, these rockers do provide quite a bit more lift.

Also they seem to have minimal effect on duration at .050" so I can pick a cam at whatever duration I want and it should be close. I will need to compensate for the higher rocker ratio to pick the lobe lift.

The other interesting thing is that neither valve hit advertised lift with the stock rockers. The intake lift is only .511" and the exhaust is .540". The cam specs are .527/.544 with a 1.7 rocker. Not sure why this is happening, except I did have to collapse the lifters to take the measurements. So possibly with the lifters pumped up the rocker ratio is a bit more since the angles change.

[chevynut]

Then why don't you buy some? Might be a better buy than a camshaft and/or lifters. Just sayin'.

I guess you can't read either.

The COMP Magnum rocker provides a higher ratio than the stock rockers and more than 1.7 full rollers, per David Vizard's testing, and they're a lot less expensive. A higher rocker ratio allows me to use a smaller lobe cam, which decreases the inertia of the lifters, possibly allowing me to use my original springs if I shim them up a bit. I have yet to read anything negative about them and they're better whan what came with the engine.

And why can't you guys understand that I don't want to change valve covers? I'd have to do that with any full roller and I don't with the COMP Magnums.

I want to get to about .600" lift. To do that I'm going to need a cam, and hopefully not new lifters. My existing lifters should work as should me existing springs. If I need to lighten anything else, I'd go with lighter retainers.

[Rick_L]

Seriously, if you had ever had your own engine with stud type rockers on a dyno and listened to it, especially on shutdown, and then heard a similar engine with shaft rockers in the same situation - you'd probably be thinking about shaft rockers. And I think it's quite possible that shaft rockers would fit under those valve covers you love so much. For whatever reason you love them.

With shaft rockers you can have just about any rocker action that tickles your fancy. Do some research. Jesel and T&D are the leading suppliers of shaft rockers, though there are others.

[55 Rescue Dog]

I guess insulting anyone that has an opinion other than yours is on topic, since now you are a self-proclaimed engine builder too. FYI, roller tipped rockers are mostly a gimmick I read about, even though I can't read. They said the roller would have to be 2 inches in diameter to equal the strength/action of a sliding/rocking tip. If roller tips are going to make a silk purse out of a sow's ear, why are they not used in the LS engines, and everything else?
Valve covers have nothing to do with engine design! A lower RPM high torque power band would make much more sense in a big cubic inch dump truck engine anyway.

[55 Rescue Dog]

Do roller tip rockers even roll? Even NASCAR 9000rpm+ engines do not use a roller tip. There is no simple answer, but easy to get it wrong. I have. There is so much more to the story than the ultimate .600 lift that is your only goal. The non roller rocker tip does not just slip, and slide, but is more like a rocking chair, which also changes the overall cam profile. The earth is no longer flat. What high power production engines use a heavy/more moving parts roller tip? All of them would, if it made a difference, I would think.

[Rick_L]

Even NASCAR 9000rpm+ engines do no use a roller tip.

Can you give more details and show an example?

I think you are wrong on this one.

[NickP]

Can you give more details and show an example?

I think you are wrong on this one.

I have to agree with you Rick. I can't speak for 2016, but all of Hendricks engines up to 2010 used T&D Roller/Shaft units.

[chevynut]

FYI, roller tipped rockers are mostly a gimmick I read about, even though I can't read. They said the roller would have to be 2 inches in diameter to equal the strength/action of a sliding/rocking tip. If roller tips are going to make a silk purse out of a sow's ear, why are they not used in the LS engines, and everything else?
Valve covers have nothing to do with engine design! A lower RPM high torque power band would make much more sense in a big cubic inch dump truck engine anyway.

I guess you just can't understand my objectives, no matter how many times I post them. This is NOT a race engine...it's a low-usage street engine. I like the looks of the stock valve covers, why can't you get that through your head? It's not about cost of new ones or anything else, I LIKE THEM. Most of the aftermarket ones suck, imo. If I could get a full roller under the valve covers I'd consider using them. I was told they wouldn't fit.

You're WRONG about roller tips...they do help. Just like everything else you get all wrong, or can't understand, you got this one wrong too. EVERY roller trunion rocker has a roller tip...why is that? The roller tip Magnum rockers are an improvement over stock stamped steel rockers. Which part of that don't you understand?

Since you're not adding anything to this thread except your BS opinions, I suggest you stop posting on it. All you do is criticize everything anyone does instead of offering constructive advice.

[NickP]

Popcorn anyone?

[chevynut]

There is so much more to the story than the ultimate .600 lift that is your only goal. The earth is no longer flat.

There's always "so much more to the story" for you as you make up "issues" and unnecessarily complicate everything. Obviously don't understand why I'm trying to get to a predicatable .600" lift. It's to address the altitude my engine needs to run at, and at the same trying to keep a moderate cam acceleration so I can use my existing springs and other components and not run into problems like spring bind, piston to valve clearance, or lifter retainer concerns. But like Mark, you just can't internalize and understand the tradeoffs and my goals. More duration at my altitude will kill cylinder pressure, so I need more lift. I don't want to rebuild the entire valvetrain and run into more issues and cost. So if you can't understand that, I can't help you. What lift would you suggest I shoot for since you seem to think you know so much?

I don't know what the shape of the earth has to do with anything.

[chevynut]

Popcorn anyone?

Isn't that the truth? These threads always degenerate when RD shows up acting like he knows everything. He can't even calculate stresses on anything much less understand a person's objectives with his project.

[chevynut]

With shaft rockers you can have just about any rocker action that tickles your fancy. Do some research. Jesel and T&D are the leading suppliers of shaft rockers, though there are others.

Sorry, I'm not going to shaft rockers....I don't need anything that exotic for a street engine especially at $1300+. :)

I did do some measuring this morning, though, which I should have done a long time ago. I'm not against full roller rockers as I've said before. I just like the stock 502 valve covers and want to keep them (something you and RD can't seem to grasp ;)). I have read that they probably won't fit under the stock valve covers so I thought I'd check for sure.

Including the gasket, the valve covers are about 2.375" deep. From the top of the head, where the gasket seals, it's 1.75" to the top of the exhaust stud, which is the tallest one. The top of the COMP rockers is 1.875", a little higher than the stud. So from the top of the stud I have about 5/8" to the bottom of the valve cover.

Now, will the COMP Pro Magnum or Ultra Pro Magnum rockers fit? I don't know. I can't find any dimensions for them. I think aluminum rockers tend to be bulkier since aluminum isn't as strong as chrome moly. But I think the issue is probably going to be the poly lock not the rocker body. I'm just not sure about what the .600" lift does. I don't know the size of the trunion or how far the stud would protrude above it either. I can get poly locks as short as .865". The studs are 7/16" so I'm guessing the trunion is at least 5/8", I guess the only way to know for sure is to try them.

Also, the Pro Magnum rockers are only available in 1.7 ratio. The Ultra Pro Magnum rockers are 1.7, 1.73, and 1.8 ratio but they're around $100 more. And I am concerned with the higher ratio that I may run into other issues like pushrod clearances but I've not seen an issue with the Magnums. Crane recommended a 1.8 rocker to me to get more lift without changing the cam. However, it would only get me to .558" lift with the stock cam so I'm not liking that solution.

[Rick_L]

I have to agree with you Rick. I can't speak for 2016, but all of Hendricks engines up to 2010 used T&D Roller/Shaft units.

Jesel is the only other supplier of rocker arm systems, unless there's a new player. There's not a single rocker arm in their catalog that doesn't have a roller tip.

The only recent change I'm aware of is the use of alloy steel rather than aluminum (at much greater expense).

[Rick_L]

Cnut, I think you're missing the correct emphasis on the high elevation recommendation. It's that you need less duration at higher elevation to maintain some cylinder pressure for a street engine. But you can run the lift you'd run with a bigger cam.

Another comment: You're fussing over .025" of max lift, but you don't even know what your heads flow! If you are going to be picky, you need all the picky details, not part of them.

[chevynut]

Cnut, I think you're missing the correct emphasis on the high elevation recommendation. It's that you need less duration at higher elevation to maintain some cylinder pressure for a street engine. But you can run the lift you'd run with a bigger cam.

The duration is part of it and a very important part. That's why I've been looking at intake closing points for various cams. But Straub and others say you need high lift too, since the duration is short, to fill the cylinder. I know lift doesn't do as good of a job of filling the cylinder as duration does, but as you said more duration causes other problems with my relatively low compression and altitude. I understand the tradeoffs.


Another comment: You're fussing over .025" of max lift, but you don't even know what your heads flow! If you are going to be picky, you need all the picky details, not part of them.

I've already posted what the heads flow. These are STOCK head flow numbers for the same heads I have.

GM #12363390 Alum Oval Port Head-stock
Intake Valve 2.250 " Exhaust (http://www.ebay.com/sch/i.html?_from=R40&_nkw=exhaust) Valve 1.800 "
Lift: inches Flow: cfm Lift:inches Flow: cfm
0.100 74.0 0.100 71.0
0.200 143.0 0.200 126.0
0.300 207.0 0.300 158.0
0.400 250.0 0.400 178.0
0.500 284.0 0.500 200.0
0.600 309.0 0.600 218.0
0.700 322.0 0.700 232.0


Vizard says BBCs need LOTS of lift because they're under-valved. I didn't want to over-do the lift so I did some investigation and as far as I can tell the heads can handle more than .600" valve lift. Haven't you been paying attention? ;)

I know heads tend to flatten out in flow at some point of valve lift, but the table doesn't seem to show that it's anywhere below .700". I don't know where the limit is as far as lift benefiting my situation but there is a physical limit. Do you have any ideas? I'd run more lift if I was confident my valvetrain would take it without throwing more money at it.

I've been trying to balance other aspects as well, like the maximum spring pressure, piston to valve clearance, coil bind, etc. Most of those aren't a problem but they can be if I don't watch out. I think .025" is a big deal because of my springs. I can get to 150 lb seat pressure and around 360 lb at .600" lift without running into any other problems. The reason I have been concerned about going higher is the rating of the COMP Magnum rockers at 350 lb max.

My intention for this engine was to disassemble it, replace the rings, clean it up, and re-assemble it. I've considered changing the cam, but didn't want it to snowball. The COMP rockers were an inexpensive, worthwhile upgrade imo.

Now I'm looking at possibly full rollers, poly locks, possibly different length pushrods to make the rockers work right, and who knows what else. What I need to be focusing on is keeping the valvetrain weight down and avoid having to change the lifters too. This could end up costing me $1500 if it gets out of hand. And it's a street engine!:eek:

[NickP]

With regards to being "picky", I haven't read all of this thread and probably will not however, I'm prone to ask questions regardless - piston to valve clearance? What do you have with stock 502 parts? Increasing the lift, be it with rocker arms or cam will shrink the clearance as I'm certain you are aware. Also, in the interest of retaining your present valve covers and possible clearance issues with any rocker changes does anyone make spacers like they used to years back? Or, can you have a set cut (laser) from bar stock?

[markm]

Good point Nick, back in the day .500 on SBC and .600 on BBC were where we started to get concerned about checking, but I am just a dummy who waste money on stuff like full roller rockers and stud girdles.

[chevynut]

With regards to being "picky", I haven't read all of this thread and probably will not however, I'm prone to ask questions regardless - piston to valve clearance? What do you have with stock 502 parts? Increasing the lift, be it with rocker arms or cam will shrink the clearance as I'm certain you are aware. Also, in the interest of retaining your present valve covers and possible clearance issues with any rocker changes does anyone make spacers like they used to years back? Or, can you have a set cut (laser) from bar stock?

Nick, piston to valve clearance doesn't seem to be an issue at this point. There was an article I posted where they put a Crane cam with .595/.610 lift and 230/236 duration into a 502 with Crane rockers and they had .150" intake valve to piston clearance. However, I don't know what the max ratio was on those rockers at full lift. I've read that you should keep .090" clearance on the intake side but some say more, some say less. The exhaust valve should have more clearance but I'm not sure why. That Crane cam had 4 degrees of advance and I'll probably go with 5 degrees....more advance means less clearance.

However, I've also read that lift doesn't have much effect on ptv clearance unless you have very long duration and that makes some sense. There seems to be opinions all over the place.

The point is these things all change when you start messing with rocker ratios and different cams.

A common thing to do to increase valve cover clearance is to use two gaskets. I could do that, but it looks to me like I don't have to. I have at least 5/8" above the stud. I can't say for sure if a full roller would work without trying it, or even if I want to go to one. Everything I read about the Magnums say they work fine for a street engine.

[chevynut]

back in the day .500 on SBC and .600 on BBC were where we started to get concerned about checking,

And that's precisely why I mentioned it, because with the varying ratio rockers and the cams that have been recommended to me I could easily be over .600" if I don't watch it. I don't think ptv clearance will be an issue with mine until around .650" lift. Then there's coil bind to watch, and I can start to have issues at around .630" with my springs shimmed to 150 lb on the seat.

All of these things limit lift, that's why I'm trying to be careful in selecting a cam and rockers. I think a .600" target is pretty reasonable and safe.

[chevynut]

Here's a pretty good article:

http://www.hotrod.com/how-to/engine/hrdp-1303-checking-piston-to-valve-clearance/

"On steel-rod engines, most engine builders like to see 0.080 inch minimum PV clearance on the intake side and 0.100 inch on the exhaust side. The big assumption, of course, is that you know or can estimate with a reasonable degree of certitude what the PV clearance was to begin with. That leads to the fundamental question you should be asking: At what point does a cam become big enough to mandate checking PV clearance? When discussing a given cam’s characteristics or “bigness,” most hot rodders and engine builders categorize a cam and its behavior in a motor in terms of the lobe duration at 0.050-inch tappet-lift (aka “duration at 0.050” or “0.050 duration”). A modern, aggressive hydraulic roller cam with Bougeant’s claimed advertised duration might have about 224/230 0.050 duration (in any event, it’ll be listed on the cam card). When choosing a new cam, its 0.050 tappet duration far outweighs gross valve lift in estimating the potential for PV-clearance issues."


Just as the rocker ratio multiplies lift, it also slightly increases the effective duration, as seen at the valve. However, cam-duration numbers on overhead-valve engines are nearly always generated at the tappet (no rocker-ratio multiplier). For the purpose of estimating whether any rocker-ratio increase makes the cam “big” enough in terms of these 0.050-tappet-duration guidelines to warrant a PV-clearance check, Comp Cam’s Billy Godbold provides this helpful hint: “Every ½-point change in rocker-arm ratio is like increasing the effective 0.050 tappet duration about 2 degrees, and every full point is worth about 3 degrees.” That means if you jumped two points (i.e., two-tenths) in ratio from 1.5:1 to 1.7:1, Godbold says the cam will behave like it has 6 more degrees of 0.050 tappet duration. I want to reiterate, however, that the actual duration numbers at the tappet don’t really change; we’re talking only about how the cam “behaves” at the valve for the purposes of establishing PV-clearance guidlelines.


These rules of thumb assume a 110-degree LSA as the baseline norm. But the narrower the LSA ground into the cam, the greater the amount of overlap near TDC and the less its inherent PV clearance. “Every time the cam grinder moves the LSA 2 degrees narrower on an otherwise equivalent cam—from 110 to 108 degrees, for example—it’s like adding 4 degrees of 0.050 duration,” Godbold explains. The opposite also holds true: A wider LSA (more than 110 degrees) increases PV clearance.


What about advancing the installed intake centerline (something that can be changed by the end user)? Every 2 degrees the intake centerline is advanced is equivalent to adding 4 degrees of 0.050 duration in terms of its effect on PV clearance for the intake valve. But this also closes the exhaust side sooner, meaning the exhaust-lobe duration, in terms of how it effects PV clearance, ends up 4 degrees milder."

[NickP]

Another concern and you may have covered it; increasing the lift shrinks the amount of clearance from bottom of retainer to top of valve guide. If you have covered that here I apologize and you may feel free in erasing this post.

[chevynut]

Nick, I've checked the retainer to valve seal distance and it's .867" so I have plenty of room there, but thanks for the input. ;)

[Rick_L]

How much "indicated" valve to piston clearance to run depends on several factors. Clearance from cylinder to cylinder can vary a lot in some instances. How you check is another factor. For instance on a solid roller cam with big springs I use the actual pieces I'm going to run, including the valve springs. With that, I run the intakes as close as .055" and the exhausts at .075". .080" intake and .100" exhaust is a good rule of thumb if you use checking springs. Maybe a bit more if you check only one cylinder. One reason I can run so close is that I check every valve, plus there's a little deflection in the valvetrain when using heavy springs. Another reason I can get away with it is that the heads will come off after the first dyno pulls to see if the valves are hitting, as well as the piston to head and piston to spark plug.

Exhausts need the extra clearance due to thermal expansion - they run much hotter than intakes.

[chevynut]

Hey RD, can you point me to some roller trunion rockers with those "rocking chair" tips for my BBC so I don't have to deal with those "gimmick" roller tips? I didn't think so.

[NickP]

If you do go to a roller tip rocker be mindful of the clearance between the underside of the rocker to the top outer edge of the retainer.

[chevynut]

Thanks Nick, I had read about that. There's all sorts of issues that can pop up in these valvetrains, like pushrods hitting the head, etc. so it's good to know about all the things to look at.

I wish the component manufacturers would publish the weights of their parts in their catalogs so you can get an idea as to what direction to go if you ned a lighter valvetrain. COMP doesn't even publish the weight of their Titanium or tool steel retainers, and they're MADE for lighter weight.

[55 Rescue Dog]

Hey RD, can you point me to some roller trunion rockers with those "rocking chair" tips for my BBC so I don't have to deal with those "gimmick" roller tips? I didn't think so.
I wish I knew. The roller trunion with a radius tip would be the perfect upgrade for a street engine. Same set up as in millions of LS engines. The problem I have with the roller tip, which I never thought about until all of the friendly discussion, is it probably just slides back and forth too, unless you are running the motor hard. And, if you ever looked at the difference in radius between the small roller, and the large radius non roller tip you would know what I mean. A big wheel rolls smoother than a little one, but in this case it is also much lighter at 6krpm, believe it or not, probably makes a difference, and the geometry is different somewhat too. Something to think about anyway.

[chevynut]

Well guys after reading Vizard's entire book on BBCs while on my vacation and your comments here, I've pretty much decided to go with full roller rockers on my 502. I just feel I'm at the limit of what the ball-type rockers can take comfortably. COMP says 350 lbs and Vizard says 375 lbs is the limit. I'm sure COMP is a little conservative, but if I need to change springs some day I don't want to be changing rockers again. Also if I plan my cam's lift to match the 1.79 ratio the roller tipped rockers deliver, it might be significantly less than that if I have to change them later. I read a few stories of guys burning the balls up and bluing the rocker cups (probably a lubrication problem). I think they're a great rocker in the right application, but a few more bucks gets me a much better set. If I'd felt they would fit under my valve covers I would have gone with the full rollers to begin with. Now I just need to verify that and decide if I'm going with 1.8 on the intakes or not.

1.8 ratio rockers will give me more lift with smaller cam lobes, which addresses a couple problems. First the lifter doesn't fall into the hole as far, and is less likely to cause problems with lifting the dogbones. Some people think that's a big problem and others don't think it's that big. Secondly, they will result in less inertia ahead of the rocker which should help as people say the "heavy" lifters are what causes valve float (I'm skeptical of that).

The downside of the 1.8 ratio is there is more spring force on the lifters, pushrods, and cam. At .600" lift I should be somewhere around 360 lbs spring pressure on the intake valves. This translates into 612 lbs at the cam for a 1.7 rocker and 648 lbs for a 1.8 rocker. Maybe the difference isn't significant. One other potential issue is pushrod clearance in the guide or head. I hope that's not a problem if I go that route. The good news is you can buy them in sets of 8.

I think I plan to get a cam recommendation from COS-Cam, through Terry Walters Performance Parts. It's a cam selection program developed by Vizard and the engineering seems sound to me. They spec the cam then buy it from any of the many vendors out there, at no additional cost.

http://www.twperformanceparts.com/index.php?route=product/category&path=982

Vizard has some very interesting comments based on his decades of experience building and testing BBCs. I didn't know he had that much experience behind him, but he claims to have run many thousands of dyno pulls testing cams and coming up with guidelines for selection. He has some very good explanations of what goes on in an engine and why overlap and LSA (LCA) are the most important factors in selecting a cam. In fact, he says the overlap period is far more critical than intake closing. He says to pick overlap based on how you intend to use the engine, and that larger engines can handle more overlap without idle issues. Then LSA is selected based on cubic inches per inch of valve diameter. According to Vizard, years of experience has shown him that the latter can be graphed as a straight line. Everything else is then fixed except lift which you can match to heads, valves, and springs.

Here's some of what he has to say about "under-valved" BBCs:

"Determining port volume is critical, so you need to know when big is just too big, matching flow curves and port voilumes to cam lift, and finally the compression ratio. Knowing where you are going an making good choices in these areas will, on a typical 496, add as much as 60 ft-lbs and 80 hp".

"Many novice Chevy big block engine builders see the big rectangular port as the horsepower maker and the oval port as its poor cousin......A factory pattern rectangular port is not the best shape to have when power is the prime requirement. ....To sum up the oval versus rectangular port debate, it's my opinion that the big factory rectangular port is a poor fix for not putting nough flow bench time into the design in the first place".

"Almost certainly, the selection of an innacurate cam is the worst mitake made when building a big block for maximum output for the application. ...You cannot necessarily avoid the incorrect cam selection bycalling a cam company for advice. Doing so still risks a 75% change of falling into a cam selection black hole. An LCS selection mistake costs a substatial amount of horsepower and torque."

"A factory 572 comes with a 112 LCA cam. Just to reinforce my point here a cam for one of my street 525s, which normally has a 107 LCA cam, was installed. This 107 LCA cam was actually shorter than the 112 unit it replaced and the overlap was less by 5 degrees. The 107 LCA cam closed he intake sooner and opened the exhaust later. Had this been on the 104-105 degree LCA cam needed for this engine, the difference would have been even more pronounced. This cam idled marginaly smoother than the 112 LCA cam.....". The engine made more torque and more HP with the 107 LCA cam.

"If you order a cam with, for example, a 106 LCA by calling your favorite cam company you may be told that having such a tight LCA for the street is not good for idle. Unfortunately, the cam tech guy has not thought things through and is just repeating what he was told. The idle quality is dependent on overlap, not LCA....If maximum power and torque are the goal, spreading the LCA to improve the idle and low-speed driveability is counter-productive. The correct answer here is not to spread the LCA but to go for LESS duration."

"Because of the Chevy big block architecture, the valve lift needed for anything other than a valvetrain with a long-duration big journal race cam plus big diameter lifters cannot be achieved. For a 496 ci engine with 2.3 intake valves and 270 degree cam, lift needs to be in the .900" range.....These engines require vry high lift for any given duration, but at shorter durations there is almost no chance of achieving anything near what the engine wants for optimal results."

Vizard has published many dyno sheets in his book. These are not all just max-horsepower builds and many were for the street. For example, he built a 468 BBC with Edelbrock E-street heads with the customer wanting decent fuel mileage, high intake vacuum, a smooth 550 RPM idle, and good towing capability. The engine was 10:1 CR and he used a 268 degree hydraulic flat tappet cam on a 107 LCA with 3 degrees of advance (Lunati profiles), and 1.8 and 1.7 rockers giving .588" lift on the intakes and .555" on the exhaust. Using an 850 holley he got 588 ft-lb and 581 HP. With a 950 plus some minor porting and a bump to 10.5:1 CR he got 611 ft-lb and 626 HP....with 468 CI at 6000 RPM.

On a 496 build he got 648 ft-lb at 4300 and 649 HP at 5800 RPM using a 284/288 cam with COMP Magnum roller tip rockers (1.79:1 max) and beehive springs for a .609" lift. The heads were Dart Iron Eagles and the engne had 10.4:1 CR. He also built a 482 that developed 678 HP, a 525 that made 756 HP, and a 510 that produced 854 HP. Of course some of these required more mods.

I'm not looking for those kinds of power numbers, but they're examples of what can be done with the right parts with cam selection being one of the most important steps...that's why I've been studying this so much and trying to decide which way to go. I'd be tickled with a 600 HP sea-level engine that made around 600 ft-lb. The short block has been together now for a while, I need to get the cam and get this thing assembled.

[chevynut]

I talked to Terry Walters yesterday about my cam selection and ordered it today. I ordered a steel billet cam because if I go with 1.8 rockers the loads on the cam will be pretty high and I don't want any problems. I won't know the cam specs until David Vizard reviews the info I submitted which includes engine and car specs, and my goals for it. After that they will call me to discuss the specs and the cam order, then they'll order it custom ground from the many cam suppliers they work with. He may also recommend some other upgrades so we'll have to discuss that.

I feel pretty confident that I'm going to get something above average and it won't be a 112 LSA cam. ;) They also price-match parts so they can get my rockers and anything else I need. I gotta get this engine back together and in the chassis, so I'm glad to finally get this rolling. I think it was worth my time to learn about cams and especially to read Vizard's book. We'll see how it goes, but I've not read anything negative about this COS-cam program anywhere.

What is COS-Cam?

It is a state-of-art Computer Optimized Spec cam selection program that was decades in the making. Built on input from thousands of dyno tests, F1 technology and some of the finest camshaft engineers across virtually the entire cam industry worldwide. Finally cam timing/event selection problems are solved with accuracy equal to extended dyno testing with a multitude of cams. But instead of days and spending thousands of dollars optimal cam selection can be done in 15 minutes - or less.


Do mainstream cam companies have an equivalent to COS-Cam?
Not really. Some of the best known cam companies have what they claim is an equivalent but the reality is that these other programs don’t even come close. But don’t take our word for it. You can establish for yourself whether or not a program has any value by doing a simple test. Give the cam company’s program an engine spec of say, a 427 inch small block Chevy and note the specs given for a so call optimal choice cam. The first thing you will find is that they often throw about 5 options at you which vary significantly in spec so it ends up with you still having to make a choice. At best, you only have a one in five chance of getting the right cam! Now re-run the program for say a 327 inch engine with only the displacement changed. The cams now recommended should be substantially different especially for the LCA as this should be 3-4 degrees wider for the smaller engine. If it is not the program is feeding you erroneous information and you will most likely end up buying a cam with the wrong specs.
If the catalog cams are not that accurate then you might feel that calling the cam company to get your cam speced would fix the problem.
Sorry, that’s another pitfall and should you doubt that try this little experiment.

Call the cam company’s tech desk and ask for your cam to be speced by one of their tech guys whose job it is to do this all day. Make a detailed note of what specs you are given. Now call two or three more cam companies for their specs and note just how much different they are!
Can they all be right? We think not. If this has not convinced you then try calling the company you originally called about a month or so later. You will almost certainly get a different cam spec even if you get the same tech guy! How can all these variations all be right?

If COS-Cam is so good why don’t we just start grinding our own cams?

Over the years our engineers have dealt with all the major reputable cam companies and one aspect has become evident. When checked out on our computerized cam dynamics checker, which checks to better than 50 millionths of an inch, we find all these cam companies are very capable (especially the US based ones) of grinding profiles with outstanding mechanical dynamics.

However not one of them has a program with the capability of COS-Cam with it’s displacement and airflow dynamics driven valve event strategies.
With so much high tech capability in terms of profile dynamics design available it just did not make sense to invest a million or so just to compete with these companies. Where they fell short was in terms of what we can call the ‘airflow dynamics’. That, in simple terms, is the optimization of the valve events to promote the highest through flow of fuel and air and the usage optimization of the post combustion cylinder pressures developed.
In that area we have no viable competition!
Even within the cam industry the critically important science of valve event driven airflow dynamics is very poorly understood. The fact that we have the unrivalled cam selection capability of COS-Cam is ironically pushing us toward being a premier cam company – all without a single cam grinder in the shop!

Why not sell the COS-Cam program to the general public?

During the development period (well in excess of twenty years) the cost of all the cam testing and associated engine building, plus the data sorting and the writing of program routines ran up costs well into the seven figure number. The bottom line is very few people can afford the resulting program price tag. Also the user needs to be trained and well versed in valve train tech as well as this programs use so that makes it less than user friendly.

So you are happy with your current cam company’s cams and don’t want to change.

We are happy with every cam company on our suppliers list. If that was not so they would be off the list in a flash thereby providing a safeguard of our customers interests. But consider this; if you call your favorite cam grinder then, at best, they will tell you what, out of their range of cams, they feel will be best for your application. What if another cam company has something that would work a little better?
Do you think that the cam company you called will tell you one of their competitors can do better? It’s doubtful.
Using COS-Cam we tell you what is likely to be the best cam regardless of who makes it. You get the choice of going with that or, if you so want, staying with your preferred cam company.

[chevynut]

I spent some time talking with David Vizard today, trying to nail down my custom cam specs. He said I have an "unusual" application and that my low compression ratio and stock GM heads would limit performance, especially at my altitude. I had thought that my 290 cc port heads with 2.25" valves would flow pretty good, but he said the flow numbers (309CFM @ .060") don't match many heads on the market today. He recommended angle milling the heads and porting them to improve CR and flow but I said I don't want to go there at this time.

We discussed my objectives again and I told him I didn't want to get into machine work at this point, and only looking to make the engine better for strictly street use without a complete replacement of all parts. He then suggested I use as thin of a head gasket as possible and get the CR as high as I can without machining. He recommended a .027" Cometic gasket in favor of the .039" stock one and said that would bump the CR to about 9.7 or up .1 point. That seems like a reasonable thing to do except I already bought my replacement head gaskets :(.

His COS-cam program says that for my CR, displacement, and valve size I should be going with a 103 LSA. Almost all of the other cam guys recommended a 112 LSA with one at 114. Only Mike Jones was at 108 and Vizard says all of them are wrong for my engine. He said Mike Jones would probably drop the LSA if he understood all of my requirements. Apparently nobody can grind a cam on a 102 lobe separation for some reason, and COMP can only grind down to a 106 LSA, so Mike Jones will be grinding my custom cam at 105 LSA which is the tightest he can go. It will be a single pattern cam with .340" lobes and 272 degrees advertised duration assuming a 1.7 rocker ratio. I don't know what the duration specs are at higher ratios but I think his book talks about it.

Rockers will be COMP full rollers (Ultra Pro Magnum/ XD) with 1.8 ratio on the intakes and either 1.7 or 1.73 on the exhausts. So my effective duration will be higher than stated. He initially recommended Scorpion aluminum rockers which give and effective 1.9 ratio but I told him I was concerned about modifications required to make them fit and preferred to stay with something less aggressive. And the chrome-moly COMP rockers should last almost forever. He said the COMP Magnums with roller tips could be made to work with the right lubricants and they won't break, but I told him I decided to go to full rollers and forget about it.

He recommended going with Mike Jones' "low travel" lifters, but I'm not sure I'm going to do that unless I absolutely have to. COMP has a set of replacement lifters Gen VI BBC that might be a good compromise if the stock ones don't work out for some reason. I didn't plan to spend $600 on new lifters :geek: but I did find this on Mike Jone's website:

"Our EHR Series Hydraulic Roller profiles are designed for the ultimate in Hydraulic Roller performance. Using our proprietary Inverse Radius technology, these EHR Series profiles offer the most area over the nose with less overlap, resulting in more horsepower and torque without sacrificing idle-smoothness and reliability. These profiles are for use with our Hydraulic Roller tappets with a .750″ – .825″ diameter wheel. These EHR Series Hydraulic Roller profiles are for use in both street and racing applications, and require the use of our high-lift hydraulic roller lifters."

I have gone through the numbers and my springs should work up to at least .650" lift before coil bind (with the .060" safety) after shimming to 150 seat pressure so I could shim them a little further for higher over-the-nose pressure if the lifters can take more seat pressure. The stock ones supposedly won't, but I'm not sure what the problem is with them.

The bottom line is that David estimates that I'll make around 640 ft-lb torque and around 550 HP at sea level. He says it should be a torque monster but the heads are the HP limiter, as well as the CR to some extent. I'm not sure I understand how that can happen when he says the torque curve should be pretty "fat". 640 torque at 5252 RPM is 640 HP so torque must drop off pretty quickly around 4500 RPM. He says a street engine lives mostly below that anyhow, and torque is why you use a big-inch engine on the street. If I were to raise the CR to around 10.5:1 by angle milling and then port the heads and do a good multi-angle valve job, I would easily be over 600 sea-level HP. Better heads would raise that further. He says anything I can do to improve airflow will increase both torque and HP using this cam, as well as going to lower elevations, so there's no downside since I don't want a high RPM engine anyhow.

I'm a little concerned that this is eventually going to lead to more parts, like pushrods or something else before I'm done, but what the hell. ;)

So here's the final cam numbers he gave me:

105 LSA
272/272 adv. duration I/E
226/226 @ .050" I/E
146/146 @ .200"
.340"/.340" lobe lift
.615" intake lift with Comp 1.8 rockers (1828)
.591 exhaust lift with COMP 1.73 rockers (1823)
ICL 101
4 degrees advance

This spec gives me 62 degrees of overlap at advertised duration which is pretty much in the range of many of the cams I've looked at, but 16 degrees overlap at .050" which is more than virtually all the other cams. David says it should idle great, but I'm puzzled by that comment. Howard's Cams grind with 61 degrees overlap says it has "fair idle" and one with 60 degrees overlap says "mildly rough idle". Maybe his idea of a smooth idle is different than mine. ;) David says he doesn't design for idle sound.

[chevynut]

Three weeks later I still don't have a cam and things pretty much fell apart. David V. got sick after we talked and dropped the ball and never sent the order to Terry Walters so he could get it to Mike Jones. Then David was unavailable for a few days to answer some questions I had regarding rockers, etc. I e-mailed Terry a week later after I found out the cam wasn't ordered and told him to go ahead with the cam order, sent him the specs David and I agreed to, and he finally ordered the cam. Mike Jones got the order and we found out that he has no 105 LSA compatible cores available and his supplier is back-ordered and can't tell him when he'll receive them. Apparently David's customers have been sucking up those cores this year.

Mike Jones has a slight disagreement with David's theory on LSA and says I don't really need an LSA that tight for what I'm trying to do. So I cancelled my order with Terry/David and discussed cam specs with Mike instead. I'll use my payment to Terry to apply toward a set of roller rockers and a pair of .027" Cometic head gaskets.

Mike and I arrived at a cam spec that he believes will work fine with my stock springs, lifters, and new roller rockers I want to install. He went with a bit more conservative profile than the one David chose, because he said with the other profile I'd have problems with my springs and lifters. He says I might have to change pushrods due to the smaller base circle, but with the thinner head gasket he's not sure. I'll have to assemble it and check. Here's what he is recommending and what I ordered last week:

108 LSA
280/280 advertised duration (.006")
226/226 @ .050"
.335"/.335" lobe lift
.603"/.570" valve lift with 1.8/1.7 rockers (nominal)

David's testing has shown that the COMP 1620 1.7 rockers deliver an actual 1.759 ratio, and the COMP 1828 1.8 ratio rockers deliver an actual 1.813 ratio. This would give me .607" lift intake and .589" lift on the exhaust. I could go with the higher 1.8 ratio on the exhaust but David said my exhaust side flows well and doesn't really need the added lift.

Mike recommended I go with Scorpion aluminum rollers, since they have a set with eight 1.8 and eight 1.7 rockers for less than the COMP rockers cost and he thinks they're better quality. The issue I have with them is that David's testing says they deliver actual 1.932 and 1.79 ratios. That would give me .647" lift intake and .599" lift exhaust. I'm afraid the intake lift would be too much. My coil bind limit with .060" margin is .645" on at least one spring when shimmed to 150 pounds on the seat. Plus the open pressure will increase on the pushrods and lifters which might lead to lifter issues. Mike thinks my lifters will work fine with 1.8 rockers, but I'm not sure about 1.9.

I've read about this ratio issue and some posts say that once the real spring is installed (instead of a checking spring) the actual observed lift is less due to valvetrain deflection. Mike says that's true, especially with aluminum rockers. It's hard to believe you can get .040" less lift from deflection. The problem is you can't predict the actual lift without trying the rockers on the engine.

So I may stick with the COMP rockers even though Mike doesn't really like them. They do have a larger shaft and bearings than most other roller rockers.

Mike says the leadtime is 2 weeks and I'll be going to Montana for a week so it should be here when I return. This whole thing has been a bit frustrating, but I felt a custom cam was reasonable for this engine to perform like I want it to.

Since I know that my springs will work with the new cam, I went ahead and re-measured them and finalized the positions of each spring, retainer, and lock on the heads. I have ordered spring ID locators and some shims which I'll need to get to 150 pounds on the seat. At .600" lift I will have an average of 366 pounds over the nose on the intakes with the 8 highest rate springs. Mike Jones says that should be enough to get to 6000 RPM with my current parts.

[chevynut]

I received my valve spring locators and tried them on the heads. Unfortunately, the spring pocket are a little smaller than 1.550" and the locators are a little bigger than that. Since the locators I found were the best fit for my heads and springs, I sanded the OD down a little to make them fit the spring pockets. I also got some more shims so now I can re-assemble my heads as soon as I find the time.

On the rockers I decided to order one of each from Summit and measure the actual lift once I get my cam. Then I can decide which set to buy and just return the single ones with my composition head gaskets for a refund. I also got some pushrod length-checker tools.

I have been told that I should get better lifters with my new cam so I asked COMP about their OEM replacements and they told me my lifters are fine at my spring pressures and theirs are essentially the same as OEM. I did a little research today based on a recommendation in David Vizard's book.

In his book, Vizard has a picture of a pair of stock Gen VI 454/502 hydraulic roller lifters and says:

"These are stock lifters as per GM Gen VI 454 or 502. Avoid their use for anything other than a 5000 RPM stock rebuild. If you want to use factory lifters get the ones used in GM's performance division's 572."

So, I looked up the part number of the Ramjet/ZZ502 lifters in the GM parts list: 17120061 (Delco HL122)

Then I looked up the part number of the 572/620 lifters in the GM parts list: 17120060 (Delco HL121)

From everything I've been able to find these lifters are the same or at least fit the same applications. Summit sells them at different prices but the descriptions are the same, and interchange listings I've found include both of them along with aftermarket replacement part numbers.

I've also been told that my lifters will start giving me problems (noise) at much over about 150 pounds on the seat. I don't understand why that happens, since there's really no pressure on the lifter when it's on the cam's base circle. Apparently there's no issue with over the nose pressures. So I dug further into it.

My springs in stock form are 140 pounds on the seat at 1.94" installed height and are part #12462970. I looked up the 572/620 springs and they're part #19172596 with 230 pounds on the seat at 2.00" installed height. That's a huge difference in both seat pressure and over the nose pressure (.632" lift). The 572/720 has solid rollers.

So I'm curious how the lifters work with that much seat pressure in the ZZ572 application if the others start making noise in the 502 application at 150+ pounds. Since they're different part numbers, could there be that much difference in the way they work? They look identical and they interchange, but Vizard seems to think the 572 lifters are better for some reason.

What would make a hydraulic lifter noisy at higher seat pressures?

[chevynut]

I can't seem to find ANYTHING about lifter noise issues at high seat pressures, but some say a hydraulic lifter won't live with seat pressures close to 200 pounds. If they can stand 400+ pounds, why can't they stand 160?

And I can't find anything explaining the difference between the OEM 17120060 and 17120061 lifters, except for a couple of other guys asking about them. I sent Vizard an e-mail asking what the difference is, since he recommends the 060 over the 061.

[chevynut]

I got the valve springs all shimmed and the heads back together today with the exception of #1 cylinder. Half of the retainer lock is screwed up....I think it may be for a 5/16" valve stem instead of 11/32" since the radius is smaller. Weird that the factory did that, as it screwed up installed height and the retainer wasn't properly locked in place. I ordered a couple of new ones and will put it together when they arrive.

I set the seat pressure at 150 pounds on all valves and used the highest rate springs on the intake valves. That took .075" more shims on the driver's head intakes except for #5 and #7 which took .060" more, and .045" more shims on the driver's head exhausts. It took .060" more shim on the passenger head intakes, and .045" on the passenger head exhaust, except for #4 which took .060" more. I have no idea how the factory determined the shims needed, but I've measured everything twice with consistent results.

Even with these shims I have well over .840" between the retainer and seals, and can go to .645" lift with a .060" minimum margin before coil bind.

I think the springs were significantly under the specified 140 pounds seat pressure. My numbers say they were in the 125 pound range on the seat which would put them at about 345 at .600". I suspect that's why guys complain about valve float under 6000 RPM with these crate engines. Glad I "blueprinted" the springs ;).

[chevynut]

I got back from vacation last night and still don't have a cam :(. Got ahold of Mike today and he informed me that his supplier was out of "stepped nose" cores that are used in the Gen VI BBC, but they're now on the way and he should be able to turn the cam around in 2 days after he gets the cores. I also got a new pair of OEM valve locks so I can finish the heads.

I tried getting information on the GM 572/620 lifters from David Vizard, since he recommended them in his book. He told me he doesn't know the difference but since GM used a big aftermarket HR cam and stiff springs with those lifters they should be "better". Not a real convincing answer. :confused:

[chevynut]

Well this is getting pretty damn frustrating :-x. I checked the valve locks and THEY DON'T FIT! The Ramjet 502 and the ZZ502 are the same base engine, and in fact mine was shipped as a ZZ502. I got the part number here, from the Chevrolet ZZ502 parts list:

https://www.chevrolet.com/content/dam/Chevrolet/northamerica/usa/nscwebsite/en/Home/Vehicles/Performance/Catalog_Download/02_pdfs/zz502-crate-engine-19201332-deluxe-specifications-1.pdf

It shows GM P/N 3947880, QTY 16, for the locks. I assumed they would come 2 per pack (since 32 are required), but I went ahead and ordered 2 anyhow from a Chevy dealer using that part number. They look similar, but not the same. Here's 3947880 and I got 2 of them, not two pairs:
http://www.crateenginedepot.com/GetImage.ashx?Path=%7E%2FAssets%2Fimages%2F3947880 _large.jpg&maintainAspectRatio=true&maxHeight=300&maxWidth=300http://www.karlperformanceparts.com/Resources/ProductImages/3947880a.jpg

I had also looked up the part number on this Chevrolet Ramjet 502 parts list, and it says "N/A" so I used the ZZ502 number:

https://www.chevrolet.com/content/dam/Chevrolet/northamerica/usa/nscwebsite/en/Home/Vehicles/Performance/Catalog_Download/02_pdfs/ramjet-502-crate-engine-12499121.pdf

I just searched for another site and found this one that lists the lock for the RJ502 as GM P/N 12366992, QTY 32 required.

http://www.crateenginedepot.com/pdfs/BB_RJ502.pdf

I have no idea why they're different, but I found a pic for 12366992:

http://i.ebayimg.com/images/g/fb8AAOSw34FVHGzC/s-l500.jpg

These look identical to the parts I have. Notice it looks like a -.050" lock, not a standard one. And it's sold as a PAIR under that part number, so why in the hell would you need 32 pairs of them as listed?

So now I have to try to find and order the right part...again. Goddam GM can't get their shit straight. :mad:

[chevynut]

Well I finally got the heads completely assembled. I got the right locks/keepers (12366992) off eBay and the heads are ready to go.

I ended up disassembling them, cleaning the ports, measuring all the springs and installed heights, shimming all valves to 150 pounds on the seat, installing internal spring locators, and replacing the seals. I really don't think I needed new seals, but I figured "might as well" ;).

I got all 5 trial rockers today and a message from Terry saying the Cometic head gaskets were shipped last week. My cam should be here this week, if Mike keeps his promised schedule.

I can't believe how damn long this stuff is taking. :cry:

http://www.trifivechevys.com/attachment.php?attachmentid=6140&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=6141&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=6142&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=6134&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=6135&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=6136&stc=1

[chevynut]

Still no cam today. Yesterday was 4 weeks since I ordered it and he quoted me 2 week turn-around. I called Mike Jones this morning and he got the core and has it rough ground. He said he still has to grind the inverse radii (all of his HR cams are IR) and finish it. He says it will ship on Monday so it will be 5 weeks by the time I get it (which is what Vizard told me). Sounds like he's swamped. :)

[Rick_L]

Here's an interesting article on the OEM Chevy lifters. Doesn't clear up any differences in the p/n's mentioned though.

http://hotrodenginetech.com/why-johnson-hydraulic-roller-lifters-belong-in-your-engine/

[chevynut]

Still no cam as of today. I'm starting to get pretty pissed off about this crap :mad:.

On June 22nd I ordered my cam, paid for it, and was quoted a 2-week turnaround. Three weeks later on July 12th I had heard nothing yet so I asked about the status and was told he didn't have any Gen VI BBC cores, but they were on the way and it would be a 2-day turn-around after they were received. IMO a core should have been ordered immediately after I placed my order. Another week later, last Friday July 21st, I called and was told the core was in, it was rough ground, and would be finished over the weekend to ship this past Monday, July 25th. Yesterday was 5 weeks from when I placed the order. I've received no notification of it being shipped, and I don't know HOW it's being shipped. If it doesn't show up by Monday, Mike is going to hear from me on and I'm not a happy camper. :mad:

I did finally get the Cometic head gaskets from Terry Walters yesterday after another delay. They were supposedly out of stock and Cometic had to make them.

While waiting for the parts I've worked on the valve covers and some more suspension parts. I still need to make sure the valve covers fit once I get the heads and rockers installed, but I went ahead and removed the powder coat by bead blasting...what a pain in the ass. Then I sanded the die casting parting lines down and smoothed them for painting. I'm probably going to leave the top raised features polished and paint the rest, so I sanded off the brushed aluminum finish scratches. ;)

Any thoughts on how to do this the easiest way? I thought I'd just prime the entire cover, sand that off on top, apply basecoat and sand again, then clearcoat. Masking doesn't seem very practical.

http://www.trifivechevys.com/attachment.php?attachmentid=6193&stc=1

[NickP]

Your image has a black box and white X but I get the gist of the question. Have you ever tried liquid masking? It's a PITA but might be a solution.

[Bluegrass Trifive]

Powder coat works well for this. I've done what you're describing by shooting powder on everything then use a modeler's brush to brush it off the features you don't want coated. Works like a charm.

[chevynut]

Mike finally came through for me and I got the cam today when I got back from elk scouting. I figured it would show up as soon as I posted about it. :D According to the packing slip he shipped the cam on Monday as he promised, but it took until today (Saturday) to get here which was 5 days. I didn't think FedEx or UPS delivered on Saturday so I expected it to arrive on Monday if it really got shipped.

One thing I noticed is that according to the cam card the base circle on the cam turned out quite a bit smaller than I expected for some reason, at only 1.180". The stock cam has a base circle of 1.296" and a .310" lobe. Seems like to go from .310" lift to .335" lift and keeping the lobe nose at the same height you would only need to make the base circle .050" smaller in diameter. So I wonder why it wasn't 1.246"??? The nose of the lobes must be at a lower height relative to the cam center but I don't know why he did that. This will probably require me to use longer pushrods now, and the lifters drop unnecessarily far into the dogbones. :(

The cam card says the ICL is 104 degrees and it's 4 degrees advanced. Intake closing is at 37 ABDC which is 3 degrees after Vizard's cam spec (primarily due to the wider LSA), but earlier than a lot of other cams I was looking at and that were recommended to me. The stock cam has an intake closing of 36 degrees.

Anyhow, I now have everything to degree the cam, check the valve lift with the various rockers, and get the rest of the engine together. I still have to order the rockers I decide to use and I may need different pushrods so I have to measure for them. I wonder how long it's going to take to get rockers now. :confused:

[chevynut]

Your image has a black box and white X but I get the gist of the question. Have you ever tried liquid masking? It's a PITA but might be a solution.

Nick, I re-loaded the pic and I hope you can see it. I don't know anything about liquid masking and don't know if it would be applicable to this job. Where can I find info on it?

[Troy]

Cnut, my dad used to paint finned oil pans, valve cover and other stuff by, if polished he would carefully apply vaseline to the polished surfaces, if sanded finish just paint and sand.

[NickP]

https://www.amazon.com/3010-Liquid-Masking-Film-16/dp/B000X4J7UW

[chevynut]

Just finished degreeing my cam and I think I have a problem :(. Maybe you guys can help me understand what's wrong...

Here's the cam card specs at .050" at the lifter:

Intake opens 9* BTDC
Intake closes 37* ABDC
Exhaust opens 45* BBDC
Exhaust closes 1* ATDC

The ICL is 104* and the ECL is 112*. LCA is 108*

The heads are off the engine. I used a steel strap with a bolt in it to locate TDC and I checked it a couple of times during the process. I set the degree wheel at TDC, set the dial indicator up on the lifter top edge and zeroed it.

Here's what I get at .050" lift at the lifter:

Intake opens 5.5* BTDC (3.5* retarded)
Intake closes 39* ABDC (2 degrees retarded)
Exhaust opens 42.5 BBDC (2.5 degrees retarded)
Exhaust closes 3* ATDC (2 degrees retarded)

From the above I get intake duration of 224.5* and an exhaust duration of 225.5* versus a spec of 226*.

I then re-measured the lobe centerlines using .150" lift on each side of the lobes and for the ICL I get 106.5* ATC (2.5 degrees retarded) and an ECL of 110* (2 degrees retarded).

So it looks like I have a retarded cam. :eek:

I know this could be the result of cam grinding error, improper dowel location, bad crank sprocket keyway location, or crank keyway location being out of spec. How do I determine which one it is? I would think Mike would use the dowel to index the cam so the lobes should be ground correctly relative to the dowel, but I don't know how they do it. I've read about dowels being off so I guess it can still happen.

What's the right way to fix this? I don't want to change my timing set because I'm pretty sure it will require me to change my timing chain cover if I do...I don't want to do that. Is an offset key the right way to fix it? Seems like it would throw the TDC mark on the damper off if I did that.

[NickP]

Degree bushing or offset key possibly for part of it. What does the cam grinder say/suggest?

[Rick_L]

Common problem, the most common error with a camshaft. Happens almost as often as not.

Fix it with an offset bushing or a timing set with multiple keyways designed for the purpose.

[chevynut]

I thought a degree bushing required a special cam sprocket. Mine has a slot in it, not a hole for the dowel.
http://allworldautomotive.com/images/userphotos/36031_62747.jpg

I don't want to have to change all that stuff. The engine has a single row timing chain and I see no reason to change it for my purposes.

I sent Mike a message asking him about the issue. I just went back and checked my TDC mark and it's still right on. I thought maybe I was looking at the wheel wrong but I wasn't. Since all the events are delayed by about two degrees I'm pretty sure my measuments are accurate.

I found an offset key on Summit Racing that says it's 2 degrees offset, but the feedback says it actually results in a 4 degree change!

https://www.summitracing.com/parts/mrg-987g

If the cam is off because of the keyway, doesn't that mean the timing mark on the damper would be off too?

[NickP]

I send those back - Summit Racing?

[chevynut]

So why is this type of timing error such a common problem? I guess I don't get it when there's a dowel in the cam that they can index off of during grinding.

I put the piston at TDC and the sprocket timing marks are perfectly aligned. When I turn it 2 degrees, the misalignment is obvous. So this tells me the cam is ground wrong because I don't believe the cam or crank sprocket is off.

I'm pretty upset about this because I asked about cam advance at least twice, and told Mike from the beginning that I didn't want to change anything in the engine, and that I had an stock non-adjustable single timing set I wanted to keep.

I sent him this in e-mail on July 12th before he even got the core:

"Hi Mike, We never discussed the ICL or advance on the cam, and I assume I install it "straight up". I don't want to change the stock timing gears for adjustable ones because that requires me to change the timing cover, and things just seem to snowball. Plus everything I have now is new."

Here's his reply today on the issue which really pisses me off after waiting 5 weeks for the cam:

'The cam is a symmetrical single pattern cam, so the exhaust lobes have to be the same size as the intake lobes. I would think the small variance is most likely from the indicator not being perfectly parallel to the lifter, and that the cam/bearing clearance could be allowing the cam to move off center. It looks like it just needs to be advanced 2 degrees.I assumed you had an adjustable timing set. Without an adjustable timing set, you'll need an offset bushing, and will have to drill out the pin hole in your timing gear. Check the link below, it has a few options, and gives instructions"


The problem is my cam sprocket won't accept a bushing, and even if it did I shouldn't have to do this imo. Also, the only 2 degree adjustable timing set I see is a COMP 7101 set but it's double row. The 3149KT is adjustable with an offset bushing and crank keyway but it's double roller too. I don't see any adjustable offset single chains.

Everything I've read says you can't use a double row timing chain on a Gen VI engine without changing the timing cover. So this is $200 for the timing set and $300 more for the cover. For a goddam 2 degree grinding error!!

I'm tempted to return the cam if I have to go through this shit. Hopefully a 2 degree offset key will work. I want Mike to explain how in the F* this happened, and WHY he ground it 2 degrees off if he did it on purpose and expected me to adjust for it.

Oh, and one more thing....I was led to believe I was getting a billet core based on the website and the pics on it...it's a cast core. I have a melonized steel gear on my distributor, so will I have to change it too?

[chevynut]

I send those back - Summit Racing?

Send what back? :confused: The timing set is stock GM that came in my engine.

[NickP]

then change it out for a single row with a hole not a slot. As a note, I'm uncertain about BBC 502 but there are also offset dowel pins for the cam.

[Rick_L]

Remember that when you're discussing cam timing, 2 degrees of crankshaft movement only results in 1 degree of camshaft movement. And also remember that your cam degreeing exercise is done in crank degrees.

I've never used an offset dowel or key, but think about it - either one is not nearly as strong as a straight pin or key. I don't know if you'd consider this an issue or not.

I don't know why you couldn't machine the slot to accept an offset bushing - the timing gear feature will then look like a keyhole. That is your cheapest out.

These things happen and they happen all the time. Like I said it's the most common camshaft error. It's your job to fix it or live with it.

[chevynut]

then change it out for a single row with a hole not a slot. As a note, I'm uncertain about BBC 502 but there are also offset dowel pins for the cam.

Do you think the slot isn't located correctly, or are you suggesting the one with a hole because I can then drill it out and use an offset bushing? Maybe I should try to borrow another timing set to see if I get the same results.

I thought about an offset dowel, but have never seen one for a cam.

Mike says in his second reply:

"Either the pin is off, or the slot is off. There's no way for you to measure it. being 2 degrees retarded means you're only one degree off at the cam, and those stock gears are often off more then 1 degree. If you can't use an offset bushing, I can offset grind the cam, so it'll check correctly with your gear. The only down side is, I'll have to reduce the base circle .015""

How can the dowel (pin) be off? Certainly he indexes off of that to grind the cam, doesn't he? How can I be sure this isn't something he ground wrong?I didn't think about it being off only one degree at the cam sprocket. A one degree offset would be about .009" at the dowel...surely they do better than that. Using the offset key on my existing timing would be the cheapest and simplest way out of this imo. I would use the non-offset key for the damper. What's wrong with doing it that way?

However, the other option MIGHT be this timing set for $104. It's a double roller and would probably be an upgrade, and it might fix this right: https://www.summitracing.com/parts/cca-7101

One of the comments says "worked and fit great ! very nice parts, high quality, I was very pleased when I open the box, its was like twice the timing chain for half the price ! it even fit under a cast alum. timing chain cover"

I just think if Mike ground this wrong he should own up to it and fix it for me without me losing anything. Hell, just shipping it back and forth is probably $40+ and I'd rather not have him re-grind it and drop the lifter further on the bore than it already is.

I tried to avoid having this snowball on me, but it looks like it's going to anyhow. :(

[chevynut]

These things happen and they happen all the time. Like I said it's the most common camshaft error. It's your job to fix it or live with it.

But is it my responsibility if the cam isn't ground correctly? If the cam grinder screws up, seems like he should fix it for me.

I still don't see why it's so common. Surely they index off of the dowel to grind the cam, right?

If the cam is ground correctly, I agree it's my job to fix it or live with it. But how do I tell?

[NickP]

A related question, what diameter degree wheel are you using? Also, everything is tight sprocket? That set you listed has plenty of direction both at the cam and at the crank, nice piece. It doesn't come with bushings though. I understand your plight. One wants perfection but when no tolerances are specked, I guess what you see is what you got. In years past, cam grinding was an art. Todays machining equipment should by all rights be better, quicker and certainly more accurate. I would pitch a fit if you paid for billet and didn't get it - thing is, are you willing to go through the whole wait period again? It's race season and anyone that does special grinds is going to pay more attention to those customers that purchase dozens rather than just one - is it right - nope but then Hillary not in jail isn't either.

[Rick_L]

I've installed probably 50 or 75 camshafts. A LOT of them have an indexing problem and no other flaws. Certain brands seem to do better than others. Crane was always spot on for me in the old days (before they went under), and most Comp cams I've used were ok too. Others not so much. Cam Dynamics (an old school brand) and older Lunati stuff come to mind.

I'm not sure why this is a problem, because like you I expect that reasonable practices should do better.

Can't really advise you on the billet vs. cast, Nick's comment about waiting more is the key there IMO. Also you are upgrading several valve train components and being picky with them - and still using the GM timing set. An upgrade there has reliability merit too besides just providing adjustability, or at least the ability to modify for adjustability.

[Rick_L]

Make sure that $104 Comp timing set is for a factory roller cam. Also the timing cover for a factory roller may be different.

[Bluegrass Trifive]

Lots of variables in play. Rod journal to the crank key, cam lobe to pin, center to center on the cam and crank bores in the block, crank gear key, lifter bore position, and cam gear pin hole, all (or a combination of) can have impact upon the cam position. I've degreed 100s of cams and more often then not they need a degree or two of adjustment. It would take precision measurement equipment to know for sure what is causing your issue. In the end it's just easier to install an offset bushing in the cam gear and move on. I usually drill the gear for a bushing on every engine I build before I final clean the parts for assembly. If you really want to get upset degree the other 7 lobes and see where they are too.

[chevynut]

A related question, what diameter degree wheel are you using?

The degree wheel is this one from Lunati... it's 9":
https://static.summitracing.com/global/images/prod/mediumlarge/lun-80000_ml.jpg

https://www.summitracing.com/parts/lun-80000/overview/


Also, everything is tight sprocket?

Everything is tight and torqued down. I have a good steel crank socket with a 1/2" square drive hole and it's tight. Everything is repeatable.


One wants perfection but when no tolerances are specked,

I know there are tolerances, but 2 degrees off seems like a lot. I guess when you figure there's some tolerance in the crank key location, keyway in the crank sprocket, the locator for the cam sprocket and the dowel relative to the cam lobes it can all add up. I still don't think it should be 2 degrees.


I would pitch a fit if you paid for billet and didn't get it

Honestly, nowhere does it say the cam is supposed to be billet...I just assumed it would be since the GM cam is billet and this one is custom. I should have asked to be sure. Although the $500 cam from Straub was SADI...some kind of cast core. I think most cams out there are cast and nobody seems to be concerned about their longevity. If I had a solid roller at .750" lift and 800 pound springs I might be more concerned. I just want to get this done.:p

[chevynut]

I've installed probably 50 or 75 camshafts. A LOT of them have an indexing problem and no other flaws. Certain brands seem to do better than others. Crane was always spot on for me in the old days (before they went under), and most Comp cams I've used were ok too. Others not so much. Cam Dynamics (an old school brand) and older Lunati stuff come to mind.

I'm not sure why this is a problem, because like you I expect that reasonable practices should do better.

Can't really advise you on the billet vs. cast, Nick's comment about waiting more is the key there IMO. Also you are upgrading several valve train components and being picky with them - and still using the GM timing set. An upgrade there has reliability merit too besides just providing adjustability, or at least the ability to modify for adjustability.

Yeah, I have calmed down a little about this today...it was just unexpected with a custom cam since I thought the tolerances would be a lot better than a production OTS grind.

What's a reasonable tolerance on this timing? I thought about 1/2 degree was what would be expected for ICL. When I found the IVO and ICL off right away, I thought I screwed up with my procedure. But after doing it again and seeing a fairly consistent 2+ degree error everywhere else I was sure something was wrong.

I am kinda shocked with what Mike told me....he says they don't index off of the dowel pin. No wonder there's so much tolerance. I guess they just assume that everyone's going to have a way to correctly time the cam.

"The cam core we start with, has the lobes roughed in on a given LSA, and centerlines.If the cam core comes with the intake centerline of 110, and we want 108, we zero it on the lobe, then move it 1 cam degree. We do not degree in off the pin, we degree in off the #1 exhaust lobe, and adjust from there. Our focus is on removing the least amount of material(heat treat) from the roughed in lobes as possible. Besides an offset key, I don't know what you can do.

I wouldn't worry about me grinding it. The lifter will only be dropping down an additional .007""

It seems ridiculous to me that they don't use the dowel as an index since that's what determines the timing in the engine. It's just common sense, isn't it? I don't understand why they do it any other way.

I now believe the cam is the culprit, not the timing set, based on Mike's reply and my observations. So it looks like my choices to fix it are to send it back and have him re-grind it 2 degrees advanced from where it is, use a 2 degree offset key (if there really is one), or try the dual roller timing set.

Grinding more could jeopardize the finish on the cam and remove the heat treat. Plus I'd probably have to pay for shipping and it still might be wrong when I get it back...who knows? And the base circle is already pretty small, imo. I have it in hand now and I guess I'd rather not wait any longer. I'm not convinced the "2 degree offset" key will work either, since two guys said it really is a 4 degree offset. They must mean 2 cam degrees or something else :confused:. If I get one and it really is 4 degrees, I'll end up 2 degrees off the other way.

I feel that GM uses pretty good parts in these crate engines, but I know a double roller chain is better than a single roller. It will probably last longer and stretch less. If it fits under my cover I'll feel okay paying the additional $104 but I'm not going to buy a new cover for $300. The fact that someone commented that the COMP timing set fit under their cast cover leads me to believe it will fit. The sprocket design shown looks like the second row is behind the front row, which is almost up against my cover now. Also, if I need 4 degrees to get everything right (since the IVO seems to be retarded 3.5 degrees), I can do that too. It just increases my flexibility and I'll decide when I check timing again.

I have to return some other stuff to Summit anyhow, so if the timing set doesn't work it can go back with those parts. And shipping it here is free.

I think I'm learning why some of these "identical" engines run 20 or more HP higher than others. It all depends on how it was put together and what the cam timing really is. Going through all of this is pretty educational for me...I had no idea a valvetrain could be this complex and hard to get right without fiddling with it. I still don't know how to check valve lift properly with my hydraulic lifters but I'll figure that out next. ;)

[chevynut]

Make sure that $104 Comp timing set is for a factory roller cam. Also the timing cover for a factory roller may be different.

My COMP catalog says it's for a "V8 454-502 Gen VI 1996-02" which all have hydraulic roller cams. There are no notes saying anything about not fitting under a stock Gen VI timing cover. It does say it comes with a roller thrust bearing which my stock one doesn't have.

[chevynut]

I've degreed 100s of cams and more often then not they need a degree or two of adjustment.

I guess that's good to know, but I didn't expect it. Normally I would think you could stick a cam in and go with it and I'll bet a lot of guys do that. But after learning that they don't index off of the dowel - the one thing that sets it's timing position in the engine - I'm not surprised.


If you really want to get upset degree the other 7 lobes and see where they are too.

I would expect them to be very close to the first ones, since they're all ground at the same time on the same setup. I'm not going to measure them. ;)

[Rick_L]

As long as the pieces are for a Gen VI engine (which had a hydraulic roller from the factory) you should be good. And perhaps that listing said that (I didn't really look, just keyed off "454" as opposed to "502". Also there are two types of roller chain used, has to do with how the pins and rollers are done. The "good" chain will cost considerably more.

The comment about the cam being finished ground NOT using the dowel pin as a reference makes sense since it is often apparent that the dowel location with respect to every cylinder is the problem.

There is another huge variable on cam timing which hasn't been brought up in the recent discussion. This has to do with the location of the lifter bores with respect to the cam tunnel. I have no idea where GM is on the quality of this with the Gen6, but it's been a huge problem in the past. What you'll see is variations from cylinder to cylinder, and intake to exhaust. Sometimes it's a whole bank of the engine, other times it's individual cylinders/valves. It is the reason that race engines and other performance builds have remachined lifter bores with bronze bushings.

[chevynut]

As long as the pieces are for a Gen VI engine (which had a hydraulic roller from the factory) you should be good. And perhaps that listing said that (I didn't really look, just keyed off "454" as opposed to "502".

Summit's website is sorely lacking in descriptions and application info, especially for the 502. I've found a lot of stuff that I have to research elsewhere to see if it fits. Jegs is even worse, imo. COMP's catalog does say it's for the 502 but Summit doesn't, they just list the Gen VI 454. I usually assume that if it fits the Gen VI 454 or Gen VI 8.1L it will fit the 502 unless it says otherwise. Since the 502 was never a production engine, it seems like it's often left out of application listings.


Also there are two types of roller chain used, has to do with how the pins and rollers are done. The "good" chain will cost considerably more.

I don't know much about that but I don't expect to run this thing at 6000 RPM very much, and I won't put 100K miles on it in my lifetime. Here's what COMP says in their catalog:

"Induction hardened and precision machined, steel billet gears for bullet proof durability. Features 9 keyway crank sprocket for 2-degree incremental adjustability, 8-degree maximum advance/retard. Pre-stretched heat-treated double roller chain w/heavy duty large pin design. Includes Torrington roller thrust bearing for reduced friction. Ideal for all street performance and race applications".


The comment about the cam being finished ground NOT using the dowel pin as a reference makes sense since it is often apparent that the dowel location with respect to every cylinder is the problem.

It's ludicrous imo that they don't use the dowel pin to index the cam when grinding. I would have never imagined they did it any other way. I guess one would have to see the grinding operation to understand why it's done like that.

Anyhow, the timing set is on the way. If it fits under my cover, I'm good to go. ;)

[Rick_L]

It's ludicrous imo that they don't use the dowel pin to index the cam when grinding. I would have never imagined they did it any other way. I guess one would have to see the grinding operation to understand why it's done like that.

Your guy did mention trying to minimize the cut to maintain base circle.

Just guessin' here, I'm thinking that the equipment used doesn't even have a provision for the dowel pin. Or another guess, the rough grind is even worse with respect to the dowel pin.

The fact that some companies' products do better at this probably also indicates some difference in the equipment used.

[Bluegrass Trifive]

As long as the pieces are for a Gen VI engine (which had a hydraulic roller from the factory) you should be good. And perhaps that listing said that (I didn't really look, just keyed off "454" as opposed to "502". Also there are two types of roller chain used, has to do with how the pins and rollers are done. The "good" chain will cost considerably more.

The comment about the cam being finished ground NOT using the dowel pin as a reference makes sense since it is often apparent that the dowel location with respect to every cylinder is the problem.

There is another huge variable on cam timing which hasn't been brought up in the recent discussion. This has to do with the location of the lifter bores with respect to the cam tunnel. I have no idea where GM is on the quality of this with the Gen6, but it's been a huge problem in the past. What you'll see is variations from cylinder to cylinder, and intake to exhaust. Sometimes it's a whole bank of the engine, other times it's individual cylinders/valves. It is the reason that race engines and other performance builds have remachined lifter bores with bronze bushings. I actually did mention the lifter bore position as a potential impacting feature. In my previous career I re-machined and installed bushing in many big and small block engines. GM's big block stuff was by far the worst of all and it wasn't unusual to see sometimes .050 to .100 deviation. My opinion is that is the most probable suspect here. If CNUT were to degree each lobe my guess is he would find some actually in spec and some others maybe even worse. As far as using the pin, I've been around most all of the common cam grinders over the years and have never seen one that doesn't reference the pin as the datum for lobe machining. In the case of cast cams there's usually two radial datums one is used for location purposes during lobe hardening and to locate radial center of lobes to drill and ream the pin hole. Once the pin hole is in either it or the installed pin then become the datum for lobe machining. We currently can easily hold +/- 1/4 of a degree according to our gauging and our Adcole Machine.

[Rick_L]

Thanks for your insight.

After some thought, I'm agreeing that you're right on the lifters bores being suspect until proven otherwise. After all the degreeing discrepancies I've seen, as well as the accompanying valve to piston clearance variation, I always check every lobe before I make conclusions, at least on a race engine.

[chevynut]

I'm not going to check every lobe, guys ;). Mike says they index off of #1 exhaust lobe, so #1 cylinder is all I'm measuring. Even if I did all of them and found discrepancies, I wouldn't do anything to fix it on this engine. I can understand it on a race engine where every HP counts.

I know there will be some slight errors in my measurements, as there probably was in the first ones. I was noticing some small discrepancies as I went around the base circle, but it could have been the lifter or who knows what else. It was perhaps a .001-.002" variation. It will be interesting to see if the new timing set changes anything. I will install it straight up first just to see if it does, then make adjustments from there.

[Bluegrass Trifive]

I'm not going to check every lobe, guys ;). Mike says they index off of #1 exhaust lobe, so #1 cylinder is all I'm measuring. Even if I did all of them and found discrepancies, I wouldn't do anything to fix it on this engine. I can understand it on a race engine where every HP counts.

I know there will be some slight errors in my measurements, as there probably was in the first ones. I was noticing some small discrepancies as I went around the base circle, but it could have been the lifter or who knows what else. It was perhaps a .001-.002" variation. It will be interesting to see if the new timing set changes anything. I will install it straight up first just to see if it does, then make adjustments from there. I agree 100%. Then offset bushing if needed.

[NickP]

I'm not going to check every lobe, guys ;). Mike says they index off of #1 exhaust lobe, so #1 cylinder is all I'm measuring. Even if I did all of them and found discrepancies, I wouldn't do anything to fix it on this engine. I can understand it on a race engine where every HP counts.

I know there will be some slight errors in my measurements, as there probably was in the first ones. I was noticing some small discrepancies as I went around the base circle, but it could have been the lifter or who knows what else. It was perhaps a .001-.002" variation. It will be interesting to see if the new timing set changes anything. I will install it straight up first just to see if it does, then make adjustments from there.

Tolerance Stack-up. When you consider every single part of the unit as a whole, the method used and the tools used to define and understand the issue, it's quite mind boggling.

[55 Rescue Dog]

That's the whole idea about even dial checking a cam, and adjusting for stack-up tolerance. I, on the other hand, not wanting to know, just set it straight up, let it go, and see how it runs. There are endless things to a good running engine on top of cam timing to chase. There is nothing wrong with attention to detail though.

[Rick_L]

I'm not going to check every lobe, guys

You have made such a big deal of the intake closing and intake centerline. You are cheating yourself not checking other cylinders and coming up with the best compromise for where the cam phasing should be based on the whole engine, not just the #1 cylinder.

Don't you realize that you've just wasted the whole exercise of getting a custom cam grind, which is probably unnecessary anyway?

You've been ranting and raving for 2 or 3 months now, and you're just going to flush it all because you don't want to do any more checking?

Once you've done the setup, it's easy to do the rest. Dead easy to do #6, but really no more trouble for the rest if you understand cam timing. There's no need to find TDC and do a degree wheel setup for every cylinder.

[chevynut]

Don't you realize that you've just wasted the whole exercise of getting a custom cam grind, which is probably unnecessary anyway?

I don't feel I've wasted anything, except possibly some time since it took three times as long as quoted to get the cam. What was I supposed to do, cancel it? I already did that once.

Try to find an OTS cam with the same specs as I got. Vizard said my engine needs a 103 LSA but we couldn't make that happen and he spec'd a 105 LSA but we couldn't get a 105 core. Mike went with 108 LSA which is what he orginally recommended to me. Vizard says the typical 112 LSA cam is not correct for big engines. I got the specs I think I need to make a ton of power and all the other cams I looked at compromised something. My goal was to get the BEST cam for MY needs and I think I got that. I increased the lift significantly and kept the duration relatively constant to maintain cylinder pressure. The overlap looks to be right where I want it for performance and idle. And the cost was comparable to many OTS cams.


You've been ranting and raving for 2 or 3 months now, and you're just going to flush it all because you don't want to do any more checking?

So asking questions and posting results is "ranting and raving"? I've been talking to experts in the field about their recommendations an making decisions about my valvetrain. I've tweaked my valve springs to a better more consistent spec, fixed a bad valve lock, and improved the spring retention. The heads are like new, but better. I have the cam ground to the specs we worked out. It's all coming together, but it's taken a long time as everything seems to. If you don't like my posts about my choices, don't read them.

I don't see what I can change if I did measure cam timing for every cylinder. I'm sure every lobe is correctly indexed to the #1 lobes, so what's the point? I really don't think this is as much of a tolerance stackup issue as it is the dowel on the cam core being off. I'll pretty much eliminate the timing set as the culprit if I install the new one and get the same results imo. I'm NOT going to machine the block to "fix" anything at this point.


Once you've done the setup, it's easy to do the rest. Dead easy to do #6, but really no more trouble for the rest if you understand cam timing. There's no need to find TDC and do a degree wheel setup for every cylinder.

What if the crank throws aren't ground exactly at 90 degrees to each other? To do it correctly you'd have to find TDC on every cylinder and a slight variation could throw the cam off too, for THAT cylinder. How do I compensate for that?

The cam is intended to be 4 degrees advanced. It's about 2 degrees advanced as it sits in the engine now. I know more advance increases low-end torque so I'm going to address that for the cylinder that the cam was ground from which should address all of them. I'm sure all the other lobes are very, very close to where they should be relative to #1 cylinder. I think 1/2 degree tolerance is close enough and probably better than most.

Lots of guys (like RD) wouldn't have even gone to as much trouble as I went to, getting the right tools to do the degreeing and valve spring setup. They would have just stuck the cam in straight up and buttoned it up. At least I'm installing it as it was intended to be installed.

If I'd decided to use the stock cam and NOT upgrade it, I most likely would have done NOTHING. So this is a big step in the right direction.

[chevynut]

I've searched and searched, and have yet to find even one reference to degreeing a cam on any more than #1 cylinder. I just don't see the point, except for being anal. :) It might be interesting, but I don't see how it really accomplishes anything from a practical point of view. Sure, you could do every cylinder and average the results but they're probably going to be within a fraction of a degree anyhow.

In my opinion, my engine is going to be far better than it was from the factory. I've addresses some of the weaknesses in the engine and found some factory defects as well. The cam will address one of the biggest criticisms I've heard about the ZZ/Ramjet 502. So all of this "ranting and raving" was worth it to me. ;)

[chevynut]

That's the whole idea about even dial checking a cam, and adjusting for stack-up tolerance. I, on the other hand, not wanting to know, just set it straight up, let it go, and see how it runs. There are endless things to a good running engine on top of cam timing to chase. There is nothing wrong with attention to detail though.

It's interesting that you're so anal about everything else, but don't even take the time to degree a cam to make sure it's installed as designed. It's probably one of the most important things relative to a strong running engine imo. If valve event timing is off, it won't run as strong as if it's right, or at least it will shift the power curve possibly to where you don't want it.

I admit that not long ago I didn't know why you needed to degree a cam, as I though you should get what you order. But after going through this I understand the importance. Every cam manufacturer recommends that you do it on installation.

[WagonCrazy]

This has been a good read to follow from an educational aspect.

[chevynut]

I got my new COMP timing set and I'm pretty impressed with the quality of it. It's a double roller, it fits perfectly, the chain is just a little tighter than the stock GM one, it has an integrated thrust roller bearing, and IT FITS UNDER MY STOCK TIMING COVER!!! :) :)

I set it up "straight up" and checked everything again. I noticed that there seems to be a very slight "dip" (.001" or so) in the cam's base circle just before the valves start to open and I think that was affecting my earlier measurements a bit since they were a little inconsistent. I assume this is due to the inverse radius ground in the cam.

So this time I made sure I was on the base circle directly opposite the lobe nose when I zeroed my indicator. Again, here is what the cam card says:

Intake opens 9* BTDC
Intake closes 37* ABDC
Exhaust opens 45* BBDC
Exhaust closes 1* ATDC

The ICL is 104* ATDC and the ECL is 112* BTDC. LCA is 108*

Here's what I get with the new timing set installed "straight up" at .050" lift at the lifter:

Intake opens 4* BTDC (5* retarded)
Intake closes 40* ABDC (3 degrees retarded)
Exhaust opens 42* BBDC (3 degrees retarded)
Exhaust closes 4* ATDC (3 degrees retarded)

So at this point my ICL is 108 degrees ATDC (retarded 4 degrees) and the ECL is 109 degrees BTDC (retarded 3 degrees). The intake duration is 224 versus a spec of 226. The exhaust duration is 226 as designed. LCA is 108.5 degrees.

I decided to advance the cam 4 degrees instead of the 2 degrees I previously measured.

Now I get these results at 4 degrees advance on the crank sprocket, and I don't think it's going to get any better. :)

Intake opens 9* BTDC (per cam spec)
Intake closes 36* ABDC (1 degree advanced)
Exhaust opens 46* BBDC (1 degree advanced)
Exhaust closes .5* ATDC (.5 degrees advanced)

The ICL is 103.5 degrees ATDC (advanced .5 degrees) and the ECL is 112.75 degrees BTDC (advanced .75 degrees). The intake duration is 225* and the exhaust duration is 226.5. LCA is calculated to be 108.125 degrees.

So everything is pretty much as designed. My measurements are probably within 1/2 degree so I think I'm good to go.

http://www.trifivechevys.com/attachment.php?attachmentid=6202&stc=1

I torqued the sprocket bolts, oiled the chain and sprockets real good, and installed the cover with some ARP stainless bolts....

http://www.trifivechevys.com/attachment.php?attachmentid=6205&stc=1

Then I did a final re-checked on all the crank and rod bolts for proper torque and installed the oilpan with ARP stainless bolts too. I seem to have misplaced one package of them so I'm using a few of the stock ones for now, until I find them or get new ones. :confused:

http://www.trifivechevys.com/attachment.php?attachmentid=6204&stc=1

Next is completion of the top end and choosing my rockers. :)

[55 Rescue Dog]

Looks great, but it brings back the memory of when I was 19 in 72 and had the bottom of a 427 all put together when I learned that NO, the oil pump shaft will not go in from the top. :confused: Also learned that the clutch fork won't go in after the bell housing and transmission are installed.

[Troy]

Then I did a final re-checked on all the crank and rod bolts for proper torque and installed the oilpan with ARP stainless bolts too. I seem to have misplaced one package of them so I'm using a few of the stock ones for now, until I find them or get new ones. :confused


I hope those missing pan bolts aren't IN the pan!!!!:eek:

[chevynut]

Thanks, yeah it's always "what did I forget?" when you button things up, isn't it? These engines have an o-ring between the rear main cap and the block...sure would be easy to forget that. :eek:

I temporarily installed the heads and torqued the driver's side head down using the old head gasket which is .012" thicker than the new Cometic MLS head gasket. I also put some clay on top of #1 piston so I can check P-V clearance when I remove it. I'll correct for the thinner head gasket.

I did some work on testing rockers and I'm a little surprised at what I found there too. I got a replacement roller lifter and gutted it, and put washers inside to make a solid lifter. It was a bitch to get the retainer back in but I got it. I used that to check valve lift.

I bought two different 1.8 rockers and 3 different 1.7 rockers. My results were far different than what David Vizard published in his book. I'm not sure why the difference, and I don't think the pushrod length would change the ratio that much.

Here's what I got on the intake and exhaust valves and actual calculated ratios:

COMP 1620 1.7 .578" intake .568" exhaust (1.710 average)
COMP 1820 1.7 .553" intake .555" exhaust (1.654 average)
Scorpion 1.7 .566" intake .566" exhaust (1.690 average)
COMP 1828 1.8 .584" intake .586" exhaust (1.746 average)
Scorpion 1.8 .611" intake .608" exhaust (1.819 average)

I'm not sure why I get slightly different results every time I do this and why the COMP 1620 rockers gave such different results on the intake versus exhaust, while the others did not. I measured all the intakes at the same time, then moved the indicator and measured all of the exhausts using the same rockers. I'll probably repeat all these measurements before I decide what to do.

David Vizard claims the COMP 1620's deliver a 1.759 ratio, the COMP 1820's a 1.707 ratio, and the COMP 1828's a 1.813 ratio. He says the Scorpion 1.7s deliver a 1.79 ratio and the 1.8s a 1.932 ratio. My numbers are lower in every case for some reason. I don't know if he used light checking springs or the actual valve springs, like I used. I don't know if pushrod length would affect the measurements that much. I used his numbers to pick the rockers to test, and now it looks like I may have to use the 1.8 ratio on both valves or a 1.73 or 1.75 ratio on the exhaust to get the lift I want. I planned to use a 1.8 rocker on the intakes anyhow.

The good news is the pushrods don't seem to hit the head where they go through the hole with the 1.8 rockers, nor do they hit the pushrod guideplate. Also, it looks like there's plenty of room above the poly nut for the valve cover, but I will probably have to remove the cast-in "drippers" inside the cover because they hit the rocker body. I'm hoping the rockers don't hit the side of the covers but I haven't looked closely at that yet.

[chevynut]

I asked Mike about my dizzy gear and whether I could use it on this cam, and he said it was okay. It's a melonized steel gear required for use with billet steel camshafts. I also asked about why the base circle ended up so small and he said the dimension on the cam card was a typo. He said it was actually 1.270". I didn't measure it so I'll assume he's correct. I did notice that the lifter didn't drop into the dogbone nearly as much as I the 1.180" would indicate.

Mike says that the exhaust lift should be 95% of the intake lift with my heads which means if I go with the Scorpion 1.8 rockers at .610 lift, I should be looking for about .580" on the exhaust. Unfortunately the Scorpion 1.7s don't get there. So I may be looking at the Scorpion 1.75 ratio for the exhausts.

The Scorpion rockers are aluminum and don't have as large of a trunion as the COMP rockers, but Mike says he thinks they're better than the COMP prts. Vizard likes them as well, and they seem to be pretty popular with a lot of guys. They make an "Endurance Series" which is for street use. The cool thing is they are offered in sets of 16 with 1.7/1.8 ratio or 1.75/1.8 ratio cheaper than buying 2 sets of 8 each. I almost ordered one 1.75 ratio Scorpion to try, but figured the 1.7s would do the trick.

https://www.summitracing.com/parts/scc-scp3064/overview/make/chevrolet

https://static.summitracing.com/global/images/prod/mediumlarge/scc-scp3000bl_sn_ml.jpg

[chevynut]

I hope those missing pan bolts aren't IN the pan!!!!:eek:

No, they are still in the ARP packaging somewhere as far as I know. The engine was upside down and I just cleaned the oilpan out really well again before I installed it. :)

[chevynut]

I just did a final rocker ratio test. I decided to quit messing around with the 1.7 rockers on the intake, since I won't be using them there. Out of 3 tests I did, I threw out the obvious few outliers and here's what I get for average lift and ratios:

COMP 1620 1.7 -----0 .574" 1.713 ratio
COMP 1820 1.7----- 0 .565" 1.686 ratio
Scorpion 1.7-------- 0 .566" 1.689 ratio
COMP 1828 1.8 -----0 .586" 1.750 ratio
Scorpion 1.8-------- 0.610" 1.820 ratio

It looks to me that the best choice would be the Scorpion 1.8 rocker on the intakes. The COMP 1828's just don't live up to what they advertise for some reason. I may be nitpicking on .017" but I wanted to get to the .603" intake lift Mike and I targeted when he spec'd the cam. Vizard was shooting for .612" and Straub .620".

Mike Jones says that my exhaust lift should be 95% of the intake lift. Vizard says in his book that BBCs run best when the exhaust lift is about .020" less than the intake lift, but I don't know why. So that means I should shoot for around .580-.590" on the exhaust if I have .610" on the intake. Unfortunately, the Scorpion 1.7s are a little low on ratio so they don't get there. As a SWAG I would guess that the Scorpion 1.75's would give .588" lift, if the ratio is in the middle of the other two. Looks like maybe a 1.73 ratio would be just about perfect, but they don't offer them for BBCs.

Now there's one other issue....the Scorpion rockers appear to need a shorter pushrod, while the COMP rockers look good. I put dry erase on the valve tips and snugged the rockers down, then turned the engine over 2 turns. Here's the results for the exhaust valve:


COMP 1820 1.7

http://www.trifivechevys.com/attachment.php?attachmentid=6209&stc=1

Comp 1620 1.7

http://www.trifivechevys.com/attachment.php?attachmentid=6210&stc=1

Scorpion 1.7

http://www.trifivechevys.com/attachment.php?attachmentid=6211&stc=1


Scorpion 1.8

http://www.trifivechevys.com/attachment.php?attachmentid=6212&stc=1

Comp 1828 1.8

http://www.trifivechevys.com/attachment.php?attachmentid=6213&stc=1

Then I set up on the intake valve and got these results:

COMP 1828

http://www.trifivechevys.com/attachment.php?attachmentid=6214&stc=1

Scorpion 1.8

http://www.trifivechevys.com/attachment.php?attachmentid=6215&stc=1


I did the above tests using a lifter that was just slightly shorter than a fully extended one. The GMPP instructions say to set the lifters at 1/8 turn past zero lash, and I thought that was pretty loose myself since that's only .006" of preload. So I think the lifter was set just about right for 1/8-1/4 turn.

The pictures above show that the witness mark is pretty good with all 3 of the COMP rockers on both intake and exhaust valves, but a little low on the valve tip with the Scorpion rockers indicating the pushrod is too long for them. I don't know how picky to get there, but everything I read says the line should be in the exact center of the valve. So if I forego a little lift, I think the COMP rockers (1820/1828) would work with the stock pushrods. I still need to install the Cometic head gasket which will change the ideal pushrod length by .012" but I don't think that's significant.

The bottom line is that if I really want to be at .600"+ lift as recommended by 3 cam experts, I need to use the Scorpion rockers. I need to make sure the Scorpions will work with my valve covers and then decide which way to go. Mike says the COMP rockers these days are poor quality and he prefers the Scorpions. But I've read good things about both of them. The COMP rockers would run $408 and the Scorpions $335 for a set of 16. The $73 difference pays for half the cost of new pushrods, so cost isn't really that big of a deal. Hell, this has already gotten way out of hand. ;)

[Rick_L]

What method are you using to determine rocker ratio? What method does Vizard use?

Something you may want to consider is measuring valve lift (and rocker ratio) at 75-85% of maximum lobe lift, in addition to maximum lobe lift (which I'm assuming you are doing now). I think this will give you a better idea of what the rocker is doing. Also, it's going to pass through the non-maximum points twice, as opposed to once for max lift.

I've never used the dry erase marker for checking the roller/valve tip contact. Looks like it leaves a readable print. Do you just paint the roller with the marker and let it transfer?

[chevynut]

What method are you using to determine rocker ratio? What method does Vizard use?

I'm measuring the actual valve lift with a dial indicator on the retainer, and as parallel to the valve stem as I can get it. The BBC has some weird angles so it's harder to do than a SBC. Then I divide the lift by the lobe height, which is .335" on both intake and exhaust.

Vizard doesn't say whether he uses actual springs or checking springs, but he did use a cam with .354" lobes and a duration of 230 degrees. The TDC lobe lift was .078". He apparently used ONE pushrod length and only checked on the intake valve. In his results table he lists the "initial ratio" which I assume is at the start of the ramp but I don't know how he calculates it. He lists the "TDC ratio", which is the actual valve lift at TDC divided by the lobe lift at TDC, and an "overall ratio" which I read to be maximum valve lift divided by lobe lift.

Mike Jones tells me that rockers deflect quite a bit under load and manufacturers factor that in to their designs. All of my rockers measured significantly lower than Vizard's which leads me to believe he used checking springs. He measured all the rockers I did, plus several more.


Something you may want to consider is measuring valve lift (and rocker ratio) at 75-85% of maximum lobe lift, in addition to maximum lobe lift (which I'm assuming you are doing now). I think this will give you a better idea of what the rocker is doing. Also, it's going to pass through the non-maximum points twice, as opposed to once for max lift.

I think maximum ratio should actually be when the rocker axis is perpendicular to the valve stem, and that should be at 50% lift. Setting the roller at the center of the valve tip should accomplish that. Straub sets up his pushrod length by putting the rocker axis perpendicular to the valve, then turning the rocker nut down 1/2 the max valve lift. Then he measures the pushrod length needed.


I've never used the dry erase marker for checking the roller/valve tip contact. Looks like it leaves a readable print. Do you just paint the roller with the marker and let it transfer?

I just used the marker to apply the ink, blow it dry for a couple seconds, put the rocker on, and turn the engine over. It also works well to just set the rocker on the valve and get a contact location which is supposed to be a little inboard of center. I find it works better than a Sharpie, which I also tried.

[chevynut]

I'm wishing the Scorpion rockers had beveled corners on them like these Crane Gold rockers do:

http://www.chevydiy.com/wp-content/uploads/2015/03/321.jpg

Not only would it make them lighter because the metal isn't needed there, but they would also clear my valve covers. :(

I found that I should have no problem with the Scorpion rockers clearing the valve covers except for #1 and #8 intakes. The back corner of the rocker hits the rocker cover slightly right at the cover screw boss/indentation at the top of the head. All of the other intake rockers are further away from the bosses and should clear the covers easily. The covers are .100" thick there and I think I can grind a little of the metal away to clear sufficiently. Even as it is, I could push the cover up as high as it will go and tighten it down and I think it clears fine. But will I remember to do that? :confused: You can see the problem area here on the second rocker (intake) that's right by the cover screw (this isn't my engine):

http://www.grumpysperformance.com/scp13.JPG

I read a lot of stuff that said the polylock nut was the issue with roller rockers and stock valve covers...I have 3/4" of clearance there checked with clay!! :) :)

So I'm going to order a 1.75 Scorpion rocker and see how it performs. If I get around .580" lift I'll call it good and order a set of 1.8/1.75 Scorpions.

I also measured what I think I need for pushrods, and that came out to be 8.563 on the intake and 7.594" on the exhaust. I adjusted a threaded pushrod checker until I got a witness mark just inboard of the cener of the valve when I wiggled the rocker, then measured the length. I'll wait til I get my 1.75 rocker to verify that on the exhaust though. What I found interesting is the Manley pushrod checker says the exhaust pushrod is just about perfect, and the intake pushrod is about 1/16" too long. I'll go with the witness mark as I think it's more accurate.

[chevynut]

Here's the pages from Vizard's book on rocker ratios:

https://books.google.com/books?id=MhDMBQAAQBAJ&pg=PA108&lpg=PA108&dq=vizard+rocker+ratio&source=bl&ots=NY4xqN4p8Q&sig=FN56yrANwgrOIE5VgZAIaNMpA2c&hl=en&sa=X&ved=0ahUKEwi1mK7kxbTOAhVYz2MKHSiIDsQQ6AEILTAB#v=on epage&q=vizard%20rocker%20ratio&f=false

[chevynut]

Just noticed that Lunati has a new line of cams.....Bootlegger Outlaw Camshafts:

http://www.bootleggercams.com/

Watch the video :)

"Lunati® Bootlegger Camshafts are an aggressive new series of cams for hot rodders that play by their own set of rules. The most powerful series of street performance cams ever produced by the Lunati design team, they build on the popular Voodoo® Series, but feature even faster opening rates, a controlled closing and far more area under the lift curve.

Bootlegger Cams are designed with a 108-degree lobe separation angle and a 104-degree intake centerline for overall nastiness that cannot be found anywhere else. This extremely aggressive design provides tons of low- and mid-range power, exactly where you need it for back road adventures and stoplight-to-stoplight performance. Even better yet, these cams also provide a killer exhaust note that sends a message before you even arrive. When put to the test on an engine dyno, Lunati Bootlegger Camshafts provide proven gains of up to 40 horsepower depending on the engine combination. Offering the perfect blend of today’s design advancements and old-school attitude, these cams embody the outlaw spirit of the bootlegger era."

Here's a video clip but I don't know which BBC cam it is: http://camshaftsounds.com/cam-video/lunati-bootlegger-489-bbc-2/

[chevynut]

The Scorpion 1.75 ratio rocker showed up while I was gone this past week. I installed it this morning on the exhaust side and checked the lift and got .584" (1.743 actual ratio). So that's what I'm going with for the exhaust rockers.

This leaves me with a final .610"/.584" I/E lift, just about where I wanted to be. :)

I've checked for clearances everywhere and I see no issues with the retainers, pushrod guides, heads, or anything else. I have plenty of space left before coil bind....gobs of it. Going to get the full set of rockers ordered tomorrow.

Just for grins I re-installed the stock GM 1.7 ratio rocker on the exhaust valve and got .565" lift (1.686 ratio) which wasn't too bad. Vizard says they're 1.679 ratio at full lift, but they perform poorly at lower lifts. So these roller rockers should be a big improvement.

I also did a quick check of the rocker sweep across the valve, and my pushrods are too long so I'll have to address that. It's about the same as the intake side. The rocker tip is about in the center of the valve with the valve closed then moves outboard as it opens.


http://www.trifivechevys.com/attachment.php?attachmentid=6231&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=6232&stc=1

[chevynut]

I removed the head today and checked the P-V clearance and was surprised at what I found. I have almost .250" clearance at the intake valve. I'm assuming this is a result of the rather short duration cam (226 degrees). This is with the .039" gasket, but I still have plenty of clearance with the .027" gasket. I know the best way to check this is with checking springs and a dial indicator but I'm not even close to having a concern.

http://www.trifivechevys.com/attachment.php?attachmentid=6233&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=6234&stc=1

I also put some clay near the top of the piston to measure quench. I roughly measured it with a steel rule at .062" with the thick gasket. I should be around .050" with the Cometic gasket. I didn't have a depth mic to check the deck so I just went with it.

http://www.trifivechevys.com/attachment.php?attachmentid=6237&stc=1

So it was good to go. I cleaned up the clay and the head and block surfaces, and installed the heads. I also installed the Energy Suspensions engine mounts with ARP Stainless bolts. Here's the Cometic gasket in place.

http://www.trifivechevys.com/attachment.php?attachmentid=6235&stc=1

I installed the head bolts with ARP Ultra Torque bolt lube and torqued the heads. Then I dug out my new set of Delco #4 Rapidfire Platinum spark plugs that Chevy recommends for this engine that have been sitting in the box for years. I checked the gaps at .040" and installed them loosely with anti-sieze to keep the bugs out. :)

http://www.trifivechevys.com/attachment.php?attachmentid=6236&stc=1

Next I need to finalize the correct pushrod lengths.:p

[chevynut]

Worked on pushrods this afternoon now that I have the right rockers, installed the Cometic gaskets, and have the heads torqued.

The stock pushrods are 7.592" intake and 8.569" exhaust. I decided to see how far off the stock pushrods would be. I didn't turn the engine over, just scrubbed the rockers on top of the valve tips that had dry-erase on them. These are the witness marks with the stock pushrods and the 1.80 and 1.75 Scorpion rockers. Notice they're below center, which means the pushrods are too long.

http://www.trifivechevys.com/attachment.php?attachmentid=6244&stc=1http://www.trifivechevys.com/attachment.php?attachmentid=6249&stc=1


I set up an adjustable pushrod at 7.50" intake and 8.44" exhaust and got these marks which look about right to me. Since they specify only 1/8 turn after zero lash (.006"), I didn't bother to factor in the lifter plunger movement as I can't even measure them that accurately:

http://www.trifivechevys.com/attachment.php?attachmentid=6245&stc=1http://www.trifivechevys.com/attachment.php?attachmentid=6250&stc=1

So it looks like the stock pushrods are about .100" too long in both cases. Time to order the correct length ones. :)

[chevynut]

This evening I decided to go ahead and install all the lifters since I didn't see any reason not to. I cleaned them, lubed them, and installed them in the engine, followed by the dogbone retainers. Then I installed the "spider" or the dogbone retainer retainer. :) :)

I also cleaned up both of the intake manifolds and did a little deburring on the lower intake. I still have to enlarge the holes in the upper intake to accept the dual 58mm throttle body. Not sure how to do that yet but I'll probaby just use a die grinder and then smooth them up. I don't know why GM didn't open the front of the intake for any aftermarket TB to fit. The teeny dual 48mm 635 CFM TB intended for a 350 was never big enough for this engine. ;)

http://www.trifivechevys.com/attachment.php?attachmentid=6246&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=6247&stc=1

[chevynut]

Got Terry checking on getting my rockers today. If he can't get them Summit has them. ;)

Having some trouble getting consensus on hydraulic lifter preload for this engine, and it will affect my pushrod length choice to some extent. GM says to go zero lash plus 1/8 turn, which is only .006" preload...that seems WAY too little to me. In the other extreme, some sources say the lifter needs to be 1/2 compressed but if I did that I'd have to add .100" preload, which is 2 full turns. Everything I've ever seen in the past suggests to go 1/2 turn past zero lash on a hydraulic lifter which would be .025". So that seems more reasonable to me.

I also did something that would make Rick proud of me :) I checked the witness mark on ever valve using the Scorpion rockers and my adjustable pushrod. Without factoring in lifter preload, it looks like about 7.50" works on every intake valve and 8.44" works on every intake valve. Unless I order custom pushrods, the closest I can get to what I need is 8.450" and 7.500" so that's what I'm going to order.

I did find this info on the lifter differences:

"MCM/MIE 454 Mag, 502 Mag & 8.2L (Gen VI) / Merc# 850466T

Single Lifter: GM #17120061

Group of 16 kit: GM #12371056 ; Chevrolet Performance : This kit includes 16 of P/N 17120061 roller tappet, 8 of P/N 12551397 tappet guides, one of P/N 12551399 tappet guide retainer, and four of P/N 9440224 retainer bolts. For single service replacement use part numbers above.

Note: these lifters differ to the Merc#850467 (GM#17120060) listed 1st above in that they supply more oil to the valvetrain."

Not sure what difference that really makes as far as use with high spring pressures.

[Bluegrass Trifive]

This GM doc shows it (page 17) using your lifter number preloaded to 1/2 turn. Look towards the end in the part number lists to confirm your part number for your lifter. https://www.chevrolet.com/content/dam/Chevrolet/northamerica/usa/nscwebsite/en/Home/Vehicles/Performance/Catalog_Download/02_pdfs/502-502-deluxe-12371204-base-12371171-engine-kit-specifications-1.pdf

[chevynut]

Thanks Bluegrass....I've seen at least 3 other sources that show 1/8 turn from zero lash. Here's one...look on page 5:

http://paceperformance.com/files/pdf/ZZ502_Long_Block.pdf

This one looks like the identical document to the one you posted, but it says 1/8 turn also on page 5.

http://www.jegs.com/InstallationInstructions/800/809/809-12371171.pdf

Your link says Rev 16JAN15 and mine says 07FEB08 so they must have changed it. The 1/2 turn makes a lot more sense. ;)

Thanks again!

[chevynut]

This is what it says for the 572/620HP Crate engine:

http://paceperformance.com/files/pdf/572_Long_Block.pdf

"Valve Lash.............................................. ..
1/8 turn down for ZZ2572/620.

[chevynut]

Well I don't think the TB is going to limit airflow now. :D

BEFORE:

http://www.trifivechevys.com/attachment.php?attachmentid=6247&stc=1

AFTER:

http://www.trifivechevys.com/attachment.php?attachmentid=6248&stc=1

[55 Rescue Dog]

Worked on pushrods this afternoon now that I have the right rockers, installed the Cometic gaskets, and have the heads torqued.

The stock pushrods are 7.592" intake and 8.569" exhaust. I decided to see how far off the stock pushrods would be. I didn't turn the engine over, just scrubbed the rockers on top of the valve tips that had dry-erase on them. These are the witness marks with the stock pushrods and the 1.80 and 1.75 Scorpion rockers. Notice they're below center, which means the pushrods are too long.

http://www.trifivechevys.com/attachment.php?attachmentid=6244&stc=1


I set up an adjustable pushrod at 7.50" intake and 8.44" exhaust and got these marks which look about right to me. Since they specify only 1/8 turn after zero lash (.006"), I didn't bother to factor in the lifter plunger movement as I can't even measure them that accurately:

http://www.trifivechevys.com/attachment.php?attachmentid=6245&stc=1

So it looks like the stock pushrods are about .100" too long in both cases. Time to order the correct length ones. :)
Seems like what would be something to think about, is sizing pushrods lengths that would put the lifter a little closer the center of travel.

[chevynut]

Seems like what would be something to think about, is sizing pushrods lengths that would put the lifter a little closer the center of travel.

GM says to preload the lifter 1/2 turn, which is .025". So that's what I'm shooting for as far as pushrod length. Ordered a set of Trickflow heat-treated 3/8" chrome-moly pushrods with .080" wall. Those should help take the increased load of the shimmed springs and 1.8 rockers without deflection.

Also found out that Terry Walters can't get them and Summit is quoting 9/30/16 on the rockers :mad:. I checked Jegs and they're $23 cheaper (usually within pennies of Summit) and they're quoting 9/1/16 shipment.

[55 Rescue Dog]

GM says to preload the lifter 1/2 turn, which is .025". So that's what I'm shooting for as far as pushrod length. Ordered a set of Trickflow heat-treated 3/8" chrome-moly pushrods with .080" wall. Those should help take the increased load of the shimmed springs and 1.8 rockers without deflection.

Also found out that Terry Walters can't get them and Summit is quoting 9/30/16 on the rockers :mad:. I checked Jegs and they're $23 cheaper (usually within pennies of Summit) and they're quoting 9/1/16 shipment.
Are you planning on firing the motor shortly after September?

[Bluegrass Trifive]

This is what it says for the 572/620HP Crate engine:

http://paceperformance.com/files/pdf/572_Long_Block.pdf

"Valve Lash.............................................. ..
1/8 turn down for ZZ2572/620. I talked to a friend today that has used a bunch of those lifters. Basically on the street he runs them at .040 and in drag stuff only about .005- .010 in an effort to minimize the impact if pump up occurs.

[Rick_L]

That makes a lot of sense and might explain some of the discrepancies in the recommendations.

[chevynut]

Are you planning on firing the motor shortly after September?

Which September? :)

I really want to get this thing put together and in the chassis so I can finish it up. I've been working on the whole cam debacle for almost 3 months now since I first contacted Vizard. It's snowballed more than I wanted it to, but I think everything is right and I'm happy with my decisions. Glad you guys pushed me to the roller rockers. I think the engine is going to be a lot better than it was out of the crate, even aside from the issues I found with it.

I'm not sure when I'm going to fire it up. I thought about doing it before I put the body on the chassis, and I see no reason that I can't. The fuel tank is in and everything is plumbed, and I have a wiring harness and ECM, and radiator/fans. Who know, I just may do it this winter.

[chevynut]

I read a lot of stuff that said the polylock nut was the issue with roller rockers and stock valve covers...I have 3/4" of clearance there checked with clay!! :) :)

Well, I don't know how the hell I measured that because it's wrong :mad:. Looks like I measured the intake side rocker by mistake. The exhaust polylocks sit a lot taller than the intakes relative to the valve cover and that's what I should have been measuring.

I got the Scorpion rockers and polylocks that came with them (1.050" long) and installed them. The valve cover doesn't fit since the polylocks just hit it. I had some 1.00" polylocks that came with the COMP rockers, and put them on. I can get the cover installed and torqued, but a couple of the polylocks still just touch the cover a bit as verified by clay wads. The polylocks only engage the stud by .300" (6 turns) when properly adjusted. That leaves .700" of polylock above the stud which is huge. I previously rough measured about .625" clearance above the top of the exhaust stud, which I thought would be plenty.

Here's the 1.050" Scorpion polylock:

http://www.trifivechevys.com/attachment.php?attachmentid=6286&stc=1

Here's the 1" COMP polylock.... I think I could go about .040" lower with the bottom of the hex and still barely clear the rocker:

http://www.trifivechevys.com/attachment.php?attachmentid=6287&stc=1

They make polylocks as short as .865" but the problem is they won't go down inside the Scorpion rocker because the polylock hex interferes with the .635" rocker opening if it's not oriented right. I considered machining some of the hex off, but they're hardened so I don't know if that would work.

Ideally I would need a polylock with a thinner hex. Crane makes some but I can't find any dimensions anywhere. Here's one that's .922" overall length that I think would work, if the hex is thinner as it looks to be.

https://static.summitracing.com/global/images/prod/mediumlarge/crn-99790-16_ml.jpg


I need a little less than .750" below the hex and the COMP polylocks are about .750". If they had a .188" thick hex instead of .250" they would work fine.

Since I was so close with the 1" COMP polylocks I decided to relieve the inside of the valve covers by milling 1" diameter by ~.050" deep pockets for the nuts. I now have plenty of clearance with the 1" COMP polylocks.

I also got the covers ground where they touched the #1 and #8 intake rocker corners, so that's fixed ;). I still wish Scorpion would put more of a bevel on the upper corners of their rockers to prevent this interference.

Now I have to order the 1" polylocks and get the valves adjusted and valve covers painted and installed, check for TDC again and install the damper, and get the intake on.

http://www.trifivechevys.com/attachment.php?attachmentid=6288&stc=1

[Rick_L]

Bevel the rockers yourself. Easy job.

[Rick_L]

Another way to fix this would be an adjuster nut that had a straight body with a hex machined on it that was smaller than the body diameter. Probably one of the first stud girdles on the market way back when had adjusters built like that (Ridgeway Racing). I probably have one in my pile of old junk somewhere. For some reason the Moroso and other popular stud girdles had a stepped body and a bigger hex.

Thing is, I don't know of anyone that makes an adjuster nut commercially for a non-stud girdle application. It seems like there might be a small market for it as you could run a shorter valve cover. I guess the business model would be bleak though.

[chevynut]

Thing is, I don't know of anyone that makes an adjuster nut commercially for a non-stud girdle application. It seems like there might be a small market for it as you could run a shorter valve cover. I guess the business model would be bleak though.

Most of the poly locks are way too short for a girdle, so your comment makes no sense to me. The nut would have to be 2" or so long for a girdle. It's probably easier to make the nut from a hex rod than to machine a smaller hex on the top like the ARP ones I posted. After searching the internet, it seems like the market for a short nut for short/stock valve covers is pretty substantial. Lots of guys are looking for ways to do it.

My COMP polylocks showed up today....they're only .050" shorter than the Scorpion ones, but they give me the clearance I need for my valve covers. I'll be installing them tomorrow and setting the lash on all the valves. Then the covers go on after they're painted which I hope to do soon (waiting on primer).

[Rick_L]

My intention was not to suggest that you use a stud girdle adjuster nut since they are WAY taller. Just to suggest that the style of that one with the small hex and straight body would solve your problem. It would clear the rocker body and could be made shorter than others. And it's no doubt more expensive to machine - but it's the way that most stud girdle nuts are made so that the stud girdle doesn't have to be taken apart to install.

[chevynut]

Today after skinning and quartering my antelope :) I prepped and primed my upper and lower intake manifolds and both valve covers. I only got the bottom of the upper intake done, but this weekend I should finish the rest of it. Then I need to spray the base and clear, hopefully next week.

[chevynut]

I finished priming the intake manifolds and valve covers and have the valve covers partially sanded. It was quite a job sanding it off and probably took an hour or more to get them smooth all the way across. My plan is to shoot the basecoat and sand it off, then get a nice smooth fine sanded surface on the aluminum and shoot clear on it. I don't know how else to do it.

I also have to sand the intakes a little before shooting the base, especially the upper one. I debated about grinding off the GM Performance Products Ramjet logo on the upper intake, but decided to leave it on.

Here's what the valve covers look like after priming and after sanding....

6364

6361

Here's the lower intake...it was really hard to get the primer in all the nooks and crannies, and it concerns me about being able to get the base and clear everywhere too. But it will be as good as I can make it and a lot of it won't be visible. :)

6362

Here's the upper intake. It was also a challenge to get primer in some spots, but hopefully they won't be very visible once the fuel rail and all the other stuff is under it.

6363

At one time I was going to have the intakes chrome plated but over the years I've seen a trend away from chrome with more painted parts. All my accessories are chrome and with some stainless brackets and the sanded valve covers it should look good. :)

[WagonCrazy]

Forward progress! lookin' good.

[chevynut]

I got some SPI Epoxy last week and re-sprayed my harmonic damper and some other parts. I found the stuff to be quite a bit different to use than the DPLF. It's thicker so I left the 2.2 tip in my primer gun and it seemed to go on heavy. After I finished I read the instructions :D and they say to use a 1.4 or 1.5 tip. I hope it's more chemical resistant when it cures, because it came off of a piece of scrap easy with acetone. I want to paint the timing numbers on the damper with white spray paint and wipe the excess off with some kind of solvent that won't attack the epoxy.

[chevynut]

I decided to try Jalapeno's suggestion on my damper and got some white latex paint for the timing marks. It didn't go as easily as it seems it should have, because the latex seemed to "stain" the epoxy. I put the latex on and immediately wiped it off with a damp cloth, but it wouldn't all come off. I still had to resort to lightly rubbing the remaining latex off with rubbing compound, but it turned out pretty good in the end.

6389

[chevynut]

I finally got all the sanding done on the intake manifolds, valve covers, and a few other parts and shot the base today. The upper intake is charcoal, just like the engine, but it will have an orange section down the center for accent to extend the orange from the radiator cover. After shooting the valve covers I had to again wet sand the base off of them before I shoot the clearcoat. I actually like the satin finish that you get with the basecoat, but since the intake needs to be gloss to match the radiator cover, and the engine block is gloss, I decided that everything needs to be gloss clear on the engine.

Here's one valve cover after shooting the PPG DBC.....not much different looking than the primer. :geek:

6396

Here it is sanded with 600:

6397

Here's the upper intake:

6398

Tomorrow morning I plan to clean up the parts really good and shoot the PPG clear. I have the heat on in the shop to make sure it's 70F in the morning. :) :)

[Tabasco]

I decided to try Jalapeno's suggestion on my damper and got some white latex paint for the timing marks. It didn't go as easily as it seems it should have, because the latex seemed to "stain" the epoxy. I put the latex on and immediately wiped it off with a damp cloth, but it wouldn't all come off. I still had to resort to lightly rubbing the remaining latex off with rubbing compound, but it turned out pretty good in the end.

6389

I'm glad you were able to make my idea work. I restored an old gas pump. The pricing numbers were a black square with recessed white numbers. I tried to paint them similar to the way you first tried with your numbers and had the same results you had. Then I came up with the latex house paint idea and that worked for me. Glad it worked for you. Looks good.

[chevynut]

Thanks for the tip Tabasco, it worked great! I got the damper back on the engine a couple days ago with an installer I borrowed from Autozone.

Today I sprayed the PPG DCU2021 clear on the upper and lower intake manifolds, valve covers, and the front swaybar. The intake manifolds were really a challenge to paint from the beginning due to all the nooks and crannies. It was a lot of work just to change the valve covers from black to dark gray. I'm pretty much an amateur painter but I think it all turned out great...we'll see when it dries and I take a good look. :)

Also cleaned the dust and gunk off of some of my Street and Performance accessory drive parts so they'll be ready to install once the engine is in the chassis. Then I'll have to get the bellhousing aligned, paint all the bellhousing parts and tranny, and put the flywheel and clutch together.

Also got a nice new Lokar dipstick today so I don't have to use the stupid-looking stock one which I have THREE of for some reason. :eek:

http://thumbs1.ebaystatic.com/d/l225/m/mMMpmeMniqDroGdWsY2ARGQ.jpg

[chevynut]

Here's a "mockup" of the intakes and the valve covers. I want to let the paint cure a few more days before I install all the bolts and tighten them down. I'll probably wait to install the upper intake when the engine is in the chassis, so I don't scratch it up with the chains. I'm also waiting for a 12-point stainless intake manifold bolt kit from ARP. :)

I'm using the stock GM intake manifolds and I noticed there's a rather large gap between the "china wall" and the manifold...around 3/16". Is that normal? None of this stuff has been machined in any way. I have some rubber gaskets from the prior aftermarket manifold that came with the engine but I read in the Ramjet Assembly Instructions to only use RTV.

I'm really liking the charcoal color on this. It will have a polished aluminum water neck, polished Edelbrock aluminum reverse rotation water pump, and an all-chrome Street and Performance accesory drive setup with A/C, PS, and 160A alternator. The throttle body is billet aluminum from Holley. I plan to put the "502" stickers on the valve covers too. :)

6399

["USA1"]

Nice tip on balancer, I have a couple degreed stockers that would work well on.

[chevynut]

Got a little more done today. I painted the ugly military green tubing on the fuel rail satin black and installed the injectors, fuel pressure regulator, and injector harness. Also installed the crank pulley, Billet Specialties water neck and PCV valve, and the GM oil cap. The MSD Blaster coil sits where the ECM usually sits on these engines. Since I got my VHX gauge set I'll install the sensors from that kit.

I'll probably install the lower intake permanently this weekend.

6405

6406

[56Chevy4Dr]

. . .

[chevynut]

The past few days I got the lower Ramjet intake manifold installed permanently and finished up everything on the topside of it. I added the home-made throttle linkage bellcrank and cable support, distributor, and stainless heater fittings. I was kind of surprised that four intake manifold bolts are not used on this intake, since they're normally where the upper intake attaches.

After lubing the rockers with oil I installed the valve covers, wire looms, and GMPP plug wires. Also cleaned up and installed the throttle body, modified and installed the IAC housing and valve, TPS, IAT sensor, and MAP sensor. Still have to get some fittings and hose/tubing for the PCV system but that's about it. I won't permanently install the upper manifold until the engine is in the chassis...or maybe until the body is on. So the engine is essentially done. :)

Next is dialing in the bellhousing for the T56, painting the bellhousing and the transmission, and getting the flywheel and clutch installed. I'll do some of that assembly with the engine in the chassis. I'll install the water pump and accessories when the engine is in the chassis too.

6429

6430

6431

[55 Rescue Dog]

Looks awesome! Just need to re-do #7 plug wire, and make it run.

[chevynut]

Thanks RD. The plug wires are from a set that is custom fit for this engine by GM Performance Parts. #7 isn't as bad as it looks, but it may be a little long. I don't know if I can shorten them or not. I think one other one is a little long too. Once it's in the chassis and the body is on I'll check it out.

[chevynut]

I just added up the rebuild costs and the total was $2173...on a BRAND NEW engine. :eek:

That was $1854 in parts and $319 in new tools I may never use again. :D Some of them are pretty worthless and some are going back to Summit. The TDC piston stop doesn't work and even got bent in my engine (read about this happening to others). The Manley pushrod length checker doesn't give the same results as the witness marks so it's going back. I ended up not even using the checking springs, but they were cheap. I also have a slew of parts to return that I tried or decided to use something else, as well as some stock 502 parts to sell that someone may want. Already had a friend ask about the cam. ;)

So here's what I ended up doing...

Torque plate hone block
New cam bearings and freeze plugs
New Total Seal standard tension piston rings
New rear main seal and rear cap o-ring
New Custom hydraulic roller cam (Mike Jones)
New COMP dual roller adjustable timing set
COMP valve spring locators and shims (150# on seat)
New Cometic MLS head gaskets
New Trickflow pushrods
New Scorpion Endurance Series aluminum roller rockers
COMP Polylocks (replaced the Scorpion set)
I pair GM valve locks (replaced damaged/wrong one)
New GM intake gaskets
Bunch of ARP stainless 12 point bolts

I re-used everything else as far as gaskets, seals, bearings, pistons, etc. I ended up changing more than I planned, which is what I was afraid of. :eek:

But it's done. :)

[56-210Sedan]

Is the R-Jet manifold painted or powder coated? Looks fantastic.

[chevynut]

Is the R-Jet manifold painted or powder coated? Looks fantastic.

Marty, the manifolds and valve covers are PPG urethane in a dark gray metallic paint. It's the same color as some of my chassis parts.

[56-210Sedan]

That turned out very nice, Good Job:cool: