I don't know the measurements off the top of my head, but the cylinder walls are much thicker than the 360 and 401. It can be safely bored 0.060 over, I think. On February 24, 2005 Steve Avery wrote: > Can 304's be made sufficiently stiff to be reliable at 500 hp ( turbo > assist) with a web rail girdle at the bottom? Also how thick is the block > between bores compared to the 390's and 401's? > Steve Avery > > > > > > > . ============================================================= Posted by wixList Archiver -- http://www.amxfiles.com/wixlist