keith blacks

The KB107's will require the block to be zero decked to bring the compression close to 10:1 and it will also require a thin head gasket. Just putting those pistons in a typical block with yield around 9.3:1, it will all be dependant on the volume of the head chambers and what machining you will do to the block and heads.

FWIW, I have a 360 with the KB107's and had the block machined for zero deck, it required about 0.020" be taken off the surface to do that. I am also using 64cc Magnum heads (J heads are around 72cc) with an 0.039" compressed head gasket, this gives me 10.6:1. I am using an XE268H cam but with the 1.6 ratio magnum rockers I have slightly more lift than the XE274 with 1.5 ratio rockers. Any case based on 1/4 trap speeds in the 102 mph region my engine is making around 370HP, I would expect yours to be similar to slightly less because of the J heads.

If your car is going to be primarily driven on the street do yourself a favor and stick with the 650 carb. I have had a Holley 600, Holley 670, Demon 725 and Holley 750 on my engine and the 670 was by far the best one. The driveability and throttle response is as good as the 600 and I do not feel a differnece on the butt dyno compared to the 725 or 750 on the top end. But the 725 and 750 definately loose a lot of throttle response at the lower rpm's.

BTW, all my 1/4 mile numbers are with the 600 and the best time is 13.7 @ 102mph with a miserable 2.2sec 60'.