I am looking at a BBC 511ci which supposedly has been made out of a 454 which has 4 bolt mains. I've never heard of this before so I'm hoping Pat or Erik will help me out? Just how far out would you have to bore a 454 to get 511ci and would the walls be paper thin? I don't want to commit myself until I know more of what I am looking at. Originally I am considering building a 496 stroker, but the price of this 511ci is very good.