If the original cylinder walls on a 250 were .160" thick (I don't know that, but that is the blueprint minimum on a Ford six and I would be surprised if the Chevy of the same era were any different) boring to 1/8 over would mean the thickness of the wall is now about 0.100 inches. That's less than 1/8 inch of unsupported cast iron cylinder wall thickness. And that assumes NO CORE SHIFT. If the core shifted by .030" then the wall is now as thin as 0.070" in some places. I've eaten kettle potatoe chips thicker than that.
