SBC 3914638 Casting ID
Posted: Mon Sep 09, 2019 3:14 pm
I have a 1968 307 block with casting number 3914638. It is a 307 for sure as bore measures 3.875". some sites say this casting is a 327 block and others say it is a 307. Is there a way to tell if there is enough wall thickness to bore to 4" without sonic checking? I have heard of some 307 blocks being able to be bored out to 4".