BBC build roller cam?

[55 Tony]

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]

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]

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 range. He had his heads flow tested 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]

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]

http://www.powerperformancenews.com/...compatibility/

http://www.enginebuildermag.com/2009...tributor-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]

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]

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]

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]

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]

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/c...?csid=388&sb=0
New cam: http://www.compcams.com/Company/CC/c...?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/c...?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?