8 inch or 9 inch?

Well, that's the idea.

 

I think 8 would be better-lighter and plenty strong. But.....everything is more expensive for 8's-posi equipment. Fewer gear selections too!

Seth

 

Although that cam is more appropriate than the 262H, I think 375hp is a bit optimistic. I think either one is a mismatch for the heads/intake. The cam is petering out just as the motor wants to really start taking off. Those lazy hydraulic flat tappet profiles just don't move enough air to make that kind of power in a 300" motor even with those heads.

If it were mine, I would ditch the hydraulic flat tappet and put in either a solid flat tappet or a hydraulic roller (I prefer mechanical cams). Either one would make quite a bit more power than a hydraulic flat tappet of the same specs because they can get away with more aggressive profiles. I would not be afraid to run something in 230-240 @.050 range and over .550 lift (if the motor is truly 9.5:1). You still probably won't be in the 375hp range but you would be a heck of a lot closer.

Edelbrock's 363hp crate engine is very similar to Jamie's combination (the cam specs are smaller but it is a hydraulic roller) and that is all they could muster with a 350 inch motor dyno-tested under ideal conditions. http://www.edelbrock.com/automotive_new/mc/crate_engines/performer_363.shtml

Also, given that the car is so light, it's a stick and traction problems are an issue, it may not be a bad idea to shift some of the power to the mid- and upper-rpm ranges. This should help mitigate some of the traction problems.

BTW, I'd try the 8" myself.

I'm not trying to be argumentative here (I wore myself out with TL), it's just my opinion.

 

I don't think an 8 inch will ever live. I have broke more than 1 with stock motors. Another thought, since your going to narrow it anyway, 8.8 can handle the power and uses less power.

 

The two main things that the 8.8 has going against it for me is that A. I don't have one just laying around already, so I would have to go find/buy one. And B. Once the gears are set up in it, it's not as easy as it would be with the 8 inch if I should decide to swap gear ratio's down the road. With an 8 inch, it's a matter of just pulling the axles and unbolting the chunk, selling it off and buying another. The 8.8 is either going to have to be totally removed from the car, or the car will have to be put on a lift, and either way a local professional will have to do it since I don't know the first thing about setting up gears. I'm not saying I would even ever swap gears, but I always try to think of any possible scenario down the road and what would be easiest for me when I'm doing something like this.

 

Then I would use a 9 inch. I just don't think a 8 inch will live very long.