So was this something done after a certain year? Or just by a certain block plant? I've never seen it on a factory built engine. The engine Chris is talking about was as built when new, Bearings were dated 2-72 so it is a virgin engine.
Not after certain year just the type of boring heads used ..Its for machining clearance ..Thats like all the square blocks by the bell housing in back of block and the dowel holes .They were used to clamp block during Machining process
