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55 Tony
12-17-2015, 06:49 PM
I had a problem in my BB which took me to taking it apart, all apart. I had a tapping noise I couldn't track down and it was driving me nuts. I found it. The windage tray came loose and was getting torn apart by #4 rod. Carefully cut the oil filter open and I hardly found traces of metal, not much on the magnetic drain plug either. Luckily I was spared, no major damage! The block is getting cleaned and just honed, crankshaft polished. I don't think the bearings were as bad as they looked in pictures but I'm not going to reuse them.

Of course I can't put it back together how it was so I'm looking to improve it. First off, it's a 1978 454 781 iron head. The factory dished pistons were at one time replaced with almost flat tops .030 over, they are beveled around the edge and I think they are 4.9cc's. So static compression is around a whopping 8:1. Truthfully I'm cheap as can be and love the fact that it runs on 87 octane even with the timing up ... around 36° if I remember correctly. It has an Edlebrock RPM performer intake and a Holley 700 mechanical secondary spreadbore, automatic with 3.42:1 gears. The cam is a comp. 11-208-3. Mild performance I think? Don't know what else I'm forgetting, oh the torque converter is supposed to be about 1000 over stock, I'm bad with numbers forget exactly. I also like not having to rev it up to move. I often doubt it's as high as it's supposed to be? I do not want to go to a higher stall converter. I'll be OK if I keep it under 6Krpm's, or less. Oh, I had 2" hookers that drug on the ground (and it's not lowered) and now I have a new set of 1 7/8" and cut out the frame horns to tuck them up high.

Anyway I've been through all different scenarios about what to do to it on a limited budget. Right now I'm thinking of a roller cam, but don't know what a good choice is. Wondering if I can do a roller cam and expect to notice a worthwhile difference leaving everything else as is. As for my driving habits, it sort of goes from WOT 0 to90 and sometimes puts around on back roads at 30mph so it would need some street manors. When I get the money, or it breaks, then maybe take a big jump to aluminum heads. Or depending on cash have the iron heads done up with larger valves? I never looked into what the iron head makeover would cost?

One thing that took a while to sink in was when I expected to see giant differences in the lift of roller cams. Then it finally hit me about the sharp ramp up and the longer duration of the valves being open almost all the way! Same lift but lots more "average" lift for lack of better terms. Am I on track here?

So, suggestions? Is this a dumb plan? The way I figure it, it's a lot easier for me to change the heads in the future than to change the cam, but will the roller cam be a waste with the 781 heads?

markm
12-18-2015, 06:43 AM
A buddy of mines 454 67 Camaro went 7.06 in the 1/8 with a .685 roller on unported 781s, I used to run 7.12 with a .595/.621 solid cam with my 75 Camaro, both cars had 2.19/1.85 valves. Both cars had forged TRW .125 domes around 9.5-10 to1. I don't believe the factory ever offered anything less than a flat top piston. For a street car I would go with a set of the aforementioned TRW/ Speedpro pistons, larger valves in your heads and a 425hp 427 solid cam. FYI my shiny new alum heads slowed my 75 Camaro down to 7.30, they required a .714 roller and 13-1 pistons to work. I run a 396 punched .060 equipped quite similar to this with a tunnel ram and two Holley 600s that eats most 454s its encountered lunch. That includes a 502 with two Edelbrocks. Your heads are fine pistons got to go.

chevynut
12-18-2015, 07:09 AM
Tony, I'm not an engine expert so I can't really answer your question about whether the heads are your power limiter because I don't know much about them. In "the old days" it seems like a cam change almost always resulted in more HP with stock heads. From what I can gather your heads are some of the best stock heads GM made. Looks like your cam has 230/230 duration at .050" and .520/.520 lift and 110* LSA which is pretty mild from what I know. Even with those same specs I think the roller will give you more power due to the quicker opening and closing ramps, but someone else more qualified than me might be able to comment on that. Be aware that with a steel roller cam you will need to change your distributor drive gear.

I think your plan of upgrading the cam now and heads later makes some sense to me. It will save having to pull the damper and timing chain.

A little googling suggests that your heads are not limiting your power:

"A stock set of 781/049's with the stock valve size is will flow around 265 cfm @.700 lift. I have a friend with a 9.5:1 468 with cleaned up 2.19 1.88 valve 781's that made 560 hp and 560 tq with an hyd roller cam in the high .240 to low .250 duration @ .050 rangehttp://images.intellitxt.com/ast/adTypes/icon1.png (http://www.hotrodders.com/forum/781-heads-71388-2.html#). He had his heads flow testedhttp://images.intellitxt.com/ast/adTypes/icon1.png (http://www.hotrodders.com/forum/781-heads-71388-2.html#) and they flowed 290 cfm @.700 lift. I have a set of 049's which are the same as the 781's that were fully ported and had a set of 2.19 1.88 valves installed. They were flow tested and flowed 325 cfm @.700 lift. In other words, you can really get some flow and hp out of these heads with a little work."

"When it comes to the amount of power a cylinder head will support, a good rule of thumb is to double the maximum airflow. Most (mild-cammed) street engines never achieve this level, while dedicated race motors can exceed this, but it’s accurate nonetheless and makes for easy math."

55 Tony
12-19-2015, 04:43 AM
Be aware that with a steel roller cam you will need to change your distributor drive gear.

I think your plan of upgrading the cam now and heads later makes some sense to me. It will save having to pull the damper and timing chain.

Good info, no one I talked to mentioned the distributor drive gear. I see composite, bronze, and steel of different types. What do I need?

Changing the cam now also saves me from pulling the water pump and radiator with tranny cooler lines and additional tranny cooler lines also. Biggest downfall to that order is getting those iron heads over the fenders without hurting anything, it may have paint by then. It's overkill but with a cherry picker right here ... Since I'm normally working by myself you use what you have to use.

chevynut
12-19-2015, 07:04 AM
http://www.powerperformancenews.com/features/twist-taking-confusion-distributor-gear-compatibility/

http://www.enginebuildermag.com/2009/07/properly-matching-your-camshaft-and-distributor-gear/

"First off, no steel distributor gear is compatible with both flat tappet and hydraulic roller cams. This is because hydraulic rollers can be made from two possible materials and either of those materials requires a different gear than the flat tappet cam. Regardless, a steel gear is not compatible with a cast iron flat tappet cam.

Distributor Gear Materials:

1. Cast Iron

2. Composite (offers great life, conforms well to the mating cam gear, and is compatible with ANY camshaft gear material)

3. Melonized or hardened steel (material that OEMs use with factory roller cams; many aftermarket distributor manufacturers use these as the default gears for their distributors)

4. Bronze (conforms well to the mating camshaft gear and will not damage the camshaft gear, but it is a self sacrificing gear intended to be used in race applications only and should be replaced about once a year)
If you have a cast iron hydraulic or solid flat tappet cam, your distributor gear options are:


1. Cast iron distributor gear

2. Composite distributor gear
If you have an austempered ductile iron hydraulic or solid roller cam, your two options are:


1. Melonized or hardened steel distributor gear

2. Composite distributor gear
If you have a billet steel hydraulic or solid roller cam, your two options are:


1. Bronze distributor gear

2. Composite distributor gear
COMP Cams recommends the composite gear because it is compatible with all camshaft gears – flat tappet, austempered cast iron cores, and billet cores. If the steel gear is not hardened, it is not compatible with either of the roller cam types.

Note: If you have an austempered core hydraulic roller cam and a .500? shaft distributor with a steel gear, verify with the manufacturer of the distributor that the steel gear they use is a melonized or hardened steel material and it will work fine.

55 Tony
12-19-2015, 08:24 AM
Thanks for the timing gear info! I'll have to see what the MSD distributor came with, I might be OK as is.

No, just looked at their website, it's hardened iron so I'll be needing one.

Rick_L
12-19-2015, 10:49 AM
Keep in mind that a low compression ratio and a big cam gives you the worst of both worlds - no low end torque as well as not realizing the top end power you could have had if you had higher compression. Raising the compression ratio fixes that on both ends.

55 Tony
12-19-2015, 07:48 PM
Keep in mind that a low compression ratio and a big cam gives you the worst of both worlds - no low end torque as well as not realizing the top end power you could have had if you had higher compression. Raising the compression ratio fixes that on both ends.

Hmm, just looked up my old cam and it says this: Hydraulic-Great for Street Machines. Use headers and 9:1 compression. In 396-402 use 2500 stall, lower gears. Rough idle.
I thought it ran fairly good for a mild cam, had great low end torque, smoked the tires no problem with 3.42 gears. Chirped 2nd at around 4k to 5krpm. Top end, well yes it was lacking, but I'm no motor head, maybe what I thought what was good was really a dog? The cam I have in mind says 9:1+ so would you think it will actually hurt the performance compared to the old cam? Or just not let it perform to near it's capacity? I could swing new pistons. Should I get some domed and if I ever get around to heads just keep them on the open side? If I shoot for 9.5:1, will it still run on 87 octane? Yes, I'm cheap and like cheap gas! By the way, damned if I can ever figure out just what "tall gears" or "lower gears" means? Seems the meaning changes depending on who's doing the talking. I thought the two where opposites. Tall meaning a physically tall ring gear and lower meaning a lower number which would probably be a lower height ring gear.

Rick_L
12-20-2015, 05:41 AM
I may have missed it, I don't think you ever said what the specs on your "old" cam and "new" cam were?

"Tall" or "high" gears are numerically lower and give you less rpm at a given speed, and less torque.

"Short" or "low" gears are numerically higher and give you more rpm at a given speed, and more torque.

55 Tony
12-20-2015, 06:45 AM
I may have missed it, I don't think you ever said what the specs on your "old" cam and "new" cam were?

"Tall" or "high" gears are numerically lower and give you less rpm at a given speed, and less torque.

"Short" or "low" gears are numerically higher and give you more rpm at a given speed, and more torque.
So I had the gear terminology backwards.

Old cam: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=388&sb=0
New cam: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=444&sb=2
New one has numerically lower lift, but with it being roller just how much of a step up is it? Or isn't it?
I'm sure you'd rather see this one, but I really hate the high stall.
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=445&sb=0
Having once ridden in a truck with a high stall converter (don't know how high it was?) I hated that it had to rev to move out of it's own way. I've never driven anything with a high stall converter and keep asking the question:

With a high stall converter, will it have to rev to near the stall speed to take off easy or moderately from a stop? Or will it just rev higher when I get on it hard? That is a major deciding factor in cam selection. I don't care at all if it revs when I nail it, I just don't want it to have to rev taking off conservatively. Or am I looking for something they don't make?

markm
12-20-2015, 08:27 AM
So I had the gear terminology backwards.

With a high stall converter, will it have to rev to near the stall speed to take off easy or moderately from a stop? Or will it just rev higher when I get on it hard? That is a major deciding factor in cam selection. I don't care at all if it revs when I
Old cam: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=388&sb=0
New cam: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=444&sb=2
New one has numerically lower lift, but with it being roller just how much of a step up is it? Or isn't it?
I'm sure you'd rather see this one, but I really hate the high stall.
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=445&sb=0
Having once ridden in a truck with a high stall converter (don't know how high it was?) I hated that it had to rev to move out of it's own way. I've never driven anything with a high stall converter and keep asking the question:
nail it, I just don't want it to have to rev taking off conservatively. Or am I looking for something they don't make?

As the owner of 3 convertors of the 4 to 5 thousand stall range, it sounds like you are describing a slipping trans more than stall speed. They will move vehicle long before rated stall speed.

Rickl is 100% correct about compression ratio, see my first reply. you need pistons more than a roller cam or aluminum heads.

Rick_L
12-20-2015, 08:50 AM
With a high stall converter, will it have to rev to near the stall speed to take off easy or moderately from a stop?

No, as markm said. But it will slip more at cruising speed.


Or will it just rev higher when I get on it hard?

Yes.

The difference between the first two cams is splitting hairs, there is simply not much difference.

The 3rd cam is more aggressive.

Seems to me that based on your expectations something smaller than the first two cams makes sense, along with a 2000 rpm stall speed converter.

55 Tony
12-20-2015, 09:37 AM
No, as markm said. But it will slip more at cruising speed.



Yes.

The difference between the first two cams is splitting hairs, there is simply not much difference.

The 3rd cam is more aggressive.

Seems to me that based on your expectations something smaller than the first two cams makes sense, along with a 2000 rpm stall speed converter.

I'm trying not to sound like an idiot but I'm afraid I'm failing badly.
Maybe I described the high stall converter wrong, it was long long ago, like over 30 years ago. I guess what I meant is that there was a lot of slipping at lower rpms. To me it sounded like the motor was working and we were hardly moving uphill and it was at low speed. (it was on back roads in the mountains)
I don't know how to take the last comment? Suggesting something smaller than I already have? No, I want more, my current cam (the first one) is in great condition, I want to change it to get more hp/torque. My current converter is supposed to be 2300 to 2500 stall speed, if it's actually as advertised, would it on fast idle at 2K going into reverse jerk and chirp the tires on a smooth garage floor? Sorry for my dumb sounding questions, I'm not a motor head and am trying to learn. If my current converter is acting as advertised, then I see no problem going a notch higher. Would going to 9.5:1 and that last cam be a worthwhile step up, maybe not for you, but for a rookie like me?

chevynut
12-20-2015, 01:46 PM
I always thought that static compression ratio was independent of head size or cam specs. How does one affect the other? Both the heads and cam affect how much air you can get into the cylinder, but compression ratio only affects how much it's squeezed. Why does a particular head or cam require a different compression ratio?

55 Tony
12-20-2015, 02:00 PM
I always thought that static compression ratio was independent of head size or cam specs. How does one affect the other? Both the heads and cam affect how much air you can get into the cylinder, but compression ratio only affects how much it's squeezed. Why does a particular head or cam require a different compression ratio?

I believe static c/r is independent of the cam, and rod length. Static compression has to figure the total area of the combustion chamber, so it's highly dependent on the head profile and how much open area there is. More area, open heads = less compression.

chevynut
12-20-2015, 02:33 PM
What I meant by "head size" was the size of the ports and valves, not the combustion chamber volume. ;)

I also don't understand why a particular cam has to have a particular stall speed converter. If it won't idle under 1000 RPM or has no torque down low, I get it...but I wouldn't get that much of a cam.

Rick_L
12-20-2015, 04:03 PM
Chevynut, the comments about compression ratio in so far in this thread are what you want, not what you have.

Compression ratio is simply the ratio of the maximum volume and the minimum volume of the cylinder. The minimum volume is the volume with the piston at top dead center, and maximum volume is the volume at bottom dead center. The minimum volume is influenced most heavily by the combustion chamber volume, but it's also affected by the piston (popup or dish and valve clearance reliefs), the deck height, the head gasket thickness, and the volume formed by the piston and cylinder down to the top ring.

The stall speeds are not what's required, but what's recommended and needed for performance. If you have a big cam that kills low end, you need a high stall converter to let you get into the range where you do make torque and power. It's not that it won't run without it, just that you won't get the full potential performance. Just like big cams kill street torque, high stall speeds slip a lot at street cruise conditions. You can go too far with both.

markm
12-21-2015, 04:17 PM
matching stall speed to cam is more important than rear gear ratio.

chevynut
12-21-2015, 06:40 PM
the comments about compression ratio in so far in this thread are what you want, not what you have.

I was referring to COMP cam's recommended use for the came. Why do they recommend a particular compression ratio with a particular cam? That's what I didn't understand. COMP says:

"Hydraulic-Great for Street Machines. Use headers and 9:1 compression. In 396-402 use 2500 stall, lower gears. Rough idle.:"

Why does 9:1 work any better than 10:1? They seem to be tying the cam to a certain compression ratio.


Compression ratio is simply the ratio of the maximum volume and the minimum volume of the cylinder.

I know what compression ratio is. ;)

Rick_L
12-22-2015, 06:03 AM
More compression ratio is always better as long as the fuel used will support it. Increased compression ratio increases performance under any operating condition. After around 13 or 14:1 the gains become close to asymptotic but they are still there.

One of the consequences of a big cam is that it lowers cylinder pressure at low rpm because the valves are open so long. So when a cam maker lists a cam as being good for 9:1 compression, they are saying that it doesn't bleed down cylinder pressure at low speeds as severely as other choices.

Dynamic compression ratio is another way of stating all this. It is an arbitrary measure of compression ratio and cam timing - an attempt to show both compression ratio need and how big the cam is. It's generally accepted that you don't want to drop much below around 8:1 dynamic compression ratio, and that around 8.5:1 is optimum for street performance. Smaller cams and higher static compression ratios are how you increase dynamic compression ratio.