Hey guys, I am in the process of building a 412 sbc. I bought pistons that are supposed to give me 9.5:1 cr. with 72cc heads, if I got 64 cc heads what would my compression ratio be with the same pistons, and would it be streetable on mid-grade gas??

 

probably closer to 11:1 but you better check with a machine shop before putting it togeter.
you could be ok w 91 octane but probably not low grade

 

The cr would be 10.27:1

Would definatly need the best premium available in your area.