Discussion Forum - Northstar Chevelle Club

If it made 450 horse and 450 torque that would make me pretty happy.

I would think 450 torque is a given with those flamed valve covers....

Going to guess at 425hp, 460 ft-lbs torque with a good carb.

Tried to build this motor like the zz430 motor gm built. This has slightly bigger cam, better intake, and comparable carb. So will see what happens.

I think it's the "port velocity" we were talking about yesterday. Over the RPM range, did it pick up or fall off more at higher RPMs? I think "too large" of a port would show itself on the lower RPMs and come into it's own at higher where the air speed through them picks up. Too large of a port doesn't help channel all that air out which affects how much air is drawn in which means the carb is under delivering based on the signal from the engine.

Short of a head swap to the other ones you were talking about (and more dyno time), maybe install it and butt dyno, then swap to 1.5 rockers and see if it butt dyno's better?

the other thing you mentioned: correction factors are different with different dynos could also come into play, though I'm sure that if Ron trusts it, it's good.

Enganeer wrote:

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What is the casting number of the heads?

Flattop pistons?

Piston to deck distance?, Quench height? Intake manifold misaligned or needs to be port matched?

After reading the article below, the numbers are pretty close.  What rpm did you stop pulling at?  The runners are big, so it going be lazy for awhile unless you really plan on winding it up.

http://www.hotrod.com/techarticles/engine/hrdp_9902_gm_small_block_cylinder_heads/

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 I don't remember the casting number of the heads but is it the ones in the article you linked to. Yes I know the big port will affect the low end torque though it really did not in that article but it still should make the same power at the top end. The motor is 0 decked with flat top two valve relief pistons and gasket thickness is 0.39 so it has quench. We pulled it to 6000 rpm and it was making peak power about 5700-5800 and peak torque around 4100-4200. All ports line up correctly I used a vortec style intake to match the taller port of those heads.

It should match this very closely http://paceperformance.com/i-5146502-gmp-12496430-1-gm-zz430-chevy-350cid-430hp-crate-engine.html and the motor made its peak numbers close to what there chart shows. I think I am going to take it to a diffferent dyno and check it again. But I am going to check compression on all cylinders and degree the cam one more time to make sure of things.