It's hard for me to say this, but I agree with Ed on that one
I poured quite a few heads in my machine shop days. Mostly S.B. Chevy's and 12 cc's ain't happenin, and not "by accident" at least as far as the Chevy's are concerned.....they ain't even close to the NHRA numbers.....I poured my LT-1 before I put it together 2 years ago...guess what.....same deal! Well under the spec......