Cam Selection
 

I'm thinking that the cam in the Chevelle needs to be a little bigger. Right now I'm running a Comp Magnum solid roller part number 11-692-8. Specs on the cam are as follows:

Lobe lift - .3666/.3666 (I run a 1.6 ratio rocker)
Dur @ .050 - 246° /246°
LSA - 110

Valve timing at .015
I/O 38 BTDC – I/C 70 ABDC
E/O 78 BBDC – E/C 30 ATDC
These specs are for 106 Intake Center Line which is what I installed it at.

I set valve lash at .018.

The specs for the engine are:

454 BBC
12.25:1 compression
Edelbrock Performer RPM heads part number 60559 with mild porting on the exhaust side. I just recently installed new valve springs that match the current cam which are part number 929-16.
Victor Jr intake with Holley 850DP built by The Carb Shop. Flow 900+ cfm.
MSD billet distributor, MSD 6AL, MSD Timing Retard
Hooker Competition headers (2inch primary 3 ½ collectors), 3inch exhaust with Flowmaster 40 series mufflers

The cars specs:

3500lbs with me in it.
TH400 with B&M Holeshot 3000 (flashes to 3600)
3.73 gears
28x10.5x15 slicks.

So what do you guys think? Do you think I’ll pick up some power with a bigger cam? My concern is that with the 3.73 gears and only a 3600 flash that I’ll loose too much bottom end and it will hurt my 60ft making the car run a slower ET but have a higher MPH because of the added upper end.

I don't know enough to give you good advice. My concern would be the same. But wouldn't a higher stall converter not cost too much for your application? Seems they should be paired: "peaky" big cam and higher stall converter. :huh:

4000 stall converters run anywhere between $1000-$1300 with the anti balloon plate. So I want to be able to work with the one I have. I think I can go a little bigger with the cam something in the range of .420-.430 lobe lift with 250-260 duration but with a split lobe favoring the exhaust side. I think I would pick up 40-50 horsepower but I wanted to get opinions. Hopefully someone has a dyno program they can run the numbers on for me.

I'm pretty sure Glenn and/or Adam has Desktop Dyno. Hit'm up on PM if they don't catch this thread.

Ron, I think the larger cam will work fine with the stall you have. The trans. brake will help you off the line. You could call my buddy Hans and ask him, he has been building alot of big block race engines the last couple of years and might have some more info. Let me know if you want his #.

I talk to you about it tonight when I get to the shop.

Can you get your converter restalled up a little? I know when I had the converter on the Camaro that was an option and was significantly less expensive than $1000.

The question I would ask is how much wheel spin do you get on the launch? If a lot, then a bigger cam can only help. You can stand to lose a touch of low end grunt, in exchange for more pull down-track. If you have little to no wheel spin..you would need a higher stall converter with a bigger cam.

Don't know BBCs, but that duration is close to mine. Since you only have RPM heads, nothing too big, I don't see a reson to go crazy with the cam. You may just be giving up low end power for high rpm power that you'll just never see if you're not spending most of your time in the 7-8K range.

If you want to do it right, have that head ported and then go with a bigger cam to match. I can shoot you a desktop dyno program if you want to play around, it's helpful if you can find the flow figures for those heads at different lift points.

I don't spin at all on just engine. Even when launching off the transbrake. My 60ft is usually in the mid 1.5 range. It will occasionally spin on the 150 shot but only if the posi doesn't hook. That's only happened around 3 or 4 times. Most of the time it hooks and I usually pull mid 1.4 60ft times. This is launching off the foot brake and activating the nitrous at full throttle.

These are the big rectangular ports with 315cc intake runners. The operating range according to Edelbrock is 2500-7000. Here's the info from Edelbrocks website including flow numbers. Remember that these numbers were before I ported the exhaust.


Highly-efficient 118cc open-style combustion chamber
High-velocity 315cc long/300cc short intake ports
Smaller-than-stock 11/32" valve stems promote excellent flow and lighter valve weight
Performer heads include drilled heat cross-over

Cylinder Head Specifications

Combustion chamber volume 118cc
Intake runner volume 315cc
Exhaust runner volume 110cc
Intake valve diameter 2.19"
Exhaust valve diameter 1.88"
Valve stem diameter 11/32"
Valve guides Manganese bronze
Deck thickness 9/16"
Valve spring diameter 1.55"
Valve spring maximum lift .700"
Rocker stud 7/16"
Guideplate Hardened steel
Pushrod diameter 3/8"
Valve angle 26°
Exhaust port location Stock
Spark plug fitment 14mm x 3/4 reach, gasket seat
Made In USA

Technical Notes: Bare heads will have valve guides & seats installed, but will require final sizing & a valve job to match the valves you will be using. Recommended spark plugs 14mm x 3/4" reach with flat gasket seat (Champion RC12YC).

Description Bare Complete
Performer RPM 454-R 60549* 60559*

Flow Numbers as tested by Edelbrock's SuperFlo SF-1020 flow bench @ 28" H2O #60559
Valve Lift / Int. / Ex.
.100 / 76 / 70
.200 / 146 / 132
.300 / 212 / 156
.400 / 255 / 181
.500 / 294 / 207
.600 / 314 / 228

I don't want to go crazy with a huge cam. My current cam pulls good to 6500 but I think the way the rest of engine is set up that I would benefit from a cam that pulled to 7000. When I dyno'd my car a few years ago when I first built the 454 it made peak torque below the 3000 starting point of the pull. That was when I had a little tighter converter that flashed to 3000. The one I have now flashes to 3600. I think a cam that makes it's peak around 4000 would wake the car up more.