i was wondering what kinda of hp and compression i will end up with if i get my heads ported and shaved to the almost their limits.(they are l26's)its a tappet motor with mild cam but will be gettin one with almost .510 and it is a '75 4boltmain bored .060 over with a 750holley Double pumper.Im just want a close estimate????????????????

 

If these are the old SBC heads (3970126) I believe they have 64cc chambers. Be very careful about porting, since some of the areas of the older castings can have very thin walls.

This '75 block, is it a 350? What pistons? There are a lot of variables that affect static compresion ratio. The more details you can offer, the easier it will be to calculate compression. As for final HP numbers, that will depend on a LOT of variables, including assembly. That's almost an impossible call.