396 chevy bore is 4.094. 427 chevy is 4.25 . Supposedly there are a few 396 blocks that can go .130 over. I havent found one.
And, a 383 mopar, with a .060 overbore and a 4.25 crank, is the exact same bore and stroke as the highly regarded 496" bbc.
Chevy changed the 396 bore in 1970 to 4.125 going .030 over. Lotsa urban myth stories like someone set the boring bar .030 over by accident and several thousand blocks went through before it was caught....blah blah blah....but the reason for it was strictly financial. The all new small block 400 debuted in 1970 and the engineers decided to jack the bore on the 396 up to 4.125 so they could use the same ring pack as the 400. They continued to market it as the 396 in cars, but 400 in trucks. Poor thing never was marketed for what it really was, a 402.
