Originally Posted by Blaze45
You could PM Irev210 or look for his B20 thread he made about the differences. I would imagine that if you switch heads that the CR would not change as the only difference I recall is that the Z had PHK pistons while the B did not.
If the head casting code is the same on both heads, I would assume that they are the same and CR would not change, but thats just me.
the P8R head has a 47cc combustion chamber... The B20 should be 45cc. You will lose a bit of compression, but IDK how much exactly. I would guess abuot 2-3 tenths.
You could deck the P8R head and maybe bring your CR back to like it was.