Quote Originally Posted by Rgtrough View Post
Hey guys, I have built a 383 cu. inch sbc to be installed in a 1974 corvette coupe with a manual transmission. The major components are:
1978 4 bolt block bored 4.030"
Scat 4340 forged 3.75" crank
Carrillo forged 6" rods Carr bolts
AFR 195 Eliminator cylinder heads
Comp Cams hyd roller cam 230/236 duration .510/.520 lift
Comp Cams 1.6 roller rockers
Edelbrock rpm performer intake
Holley 4150 carb 750 cfm
Using 1 5/8" dyno headers this engine make 479 ft/lb @ 4400 and 468 hp @ 5800.
What effect will running 1 7/8" primaries into a 4" collector headers have on these results. Also I don't think the RPM intake will fit under my stock L82 hood. Can you see what the results would be with a Wiend low rise single plane Stealth intake.
Thanks for you help
You're a little mixed up on your manifolds. The Stealth is a dual-plane hi-rise. Here's the rundown on Weiand intakes....
#8120 Action Plus...low rise dual plane, height front 3.50", height rear 4.50", idle to 5500. (Same manifold as Edelbrock Performer).
#8150 Stealth....high rise dual plane, height front 4.19", height rear 5.27", 1500 to 6700. (Same manifold as Edelbrock Performer RPM).

It is my opinion that if you use a single plane intake, you're going to shoot yourself in the foot. Every dyno test I have assembled has shown more hp and torque from idle to 6000 with a dual-plane, high-rise intake. Over 6000, a single-plane intake makes more power and that's great for a circle track car. It just doesn't work too well on a street driver where the motor is operated under 6000 for 99.9% of the time.

Changing from a high-rise to a low-rise dual plane has shown to drop 40-60 hp on the dyno. Going to larger primaries on the headers will drop torque at lower rpm's, but you'll pick up a little power at the top.

List your static compression ratio and I'll run it up on the DynoSim.