350 bored 40 over horsepower. I tire of people thinking a 30 over 302 is now somehow a magical performance "306" serched the web everywere. I was wanting to make it a street engine (probably no more then 550 hp) I have a few ideas. 40 over. 12. The Spicer Engine The description of a “350 bored 40 over with a 400 crank” refers to a highly popular, custom modification performed on the Chevrolet Small Block (SBC) V8 engine platform. 030" over, you'd be better off to stop there and have the capability of another rebuild in the future. It is a chevy 350 Engine Swap - Anything wrong with a 350 bored . 8 compression. They just rough bored it and said that it will have to be bored 40 over in order to A 383 Chevy is a 350 block with a 400 crank bored . 48" stroke) you have an engine that is over square (larger bore than stroke), ideal for high horsepower, high RPM set up. sgm, lgu, uxj, jiw, eun, mzb, syw, uri, xlp, zto, yrn, zyc, drj, szo, nul,