340 compression ratio

scatpackbee said
My factory '69 x heads cc'd at 75.

I didn't think it was possible to be so far away from the advertised 63 CCs but Herb McCandless confirmed the fact that x heads were more like 75 CCs on one of his performance seminars.

I milled mine down to get 68 CCs for a true 9.8-1 compression ratio.

My 340 X heads averaged @ 68 CC, my set of J, 2.02 averaged 73 CC. The vender I bought the J heads from said they were milled .030", doesn't appear they were to me.
uempistons.com has a pretty good compression ratio calculator. It does static, and dynamic.