I've read a lot of articles about the differences between the B20F heads and the B20E heads. I have to late F heads with from '74 140s. I was told these are the better of the two F heads as they already have hardened valve seats.

One is built and ready to go on the car for a while. The other is going to be disassembled, shaved, ported, and put back together with some double valve springs and other new components.

What I'm wondering is how much you would have to shave off of an F head to bring it up to E head compression specs. I know this requires measuring and mocking up and I will be doing that as well. I just need some numbers to go by so I'll know if my math is correct. I want to start with a stock head gasket and work my way down from there if needed.

So basically if you had two completely new, never-installed heads, one E and one F, how much shorter would the E head be?