Reply to "More Info Needed for Aussie Head Swap"

Ron

The Australian 302C heads have a nominal 57.9 cc combustion chamber volume. If you do the math you'll find even with that small chamber a 302 cubic inch motor with flat top pistons will only have about 9.2:1 compression ratio. The combustion chamber volume of the Boss 302 heads was similar, at 58.5 cc nominal. I think the confusion about the volume of the 302C combustion chambers stems from the fact that Ford SVO/Motorsport rated the the closed chamber 2V heads they sold in the US at 62 cc (SVO part number M-6049-C351).

A 351 cubic inch motor with flat top pistons and 58 cc heads will yield about 10.6:1 compression ratio. Your 0.030" over motor would be a bit more than that. To operate the motor on pump gas you'll need a cam with about 245 degrees intake duration (at 0.050" lift) and there goes your low end grunt you're looking for.

I'm not going to try and talk you out of anything or second guess you, but I have one question: must you use the iron 302C heads you purchased, or would you consider a set of alloy 2V heads for your project? My reasoning is thus: by the time you've set up a set of iron heads with the good valves, springs, porting etc, you have spent a fair sum of money but still have heads that perform worse than a set of alloy 2V heads from Trick Flow, AFD or CHI out of the box. The alloy heads will tolerate more compression and have slightly larger combustion chambers. You'll be able to run a milder cam with the alloy heads.