I have a buick 455 bored 30 over. Had a pistom crack (valves ate the ring also)and scratch it's cylinder. Used a Hone to remove the scratches. The Bore is now 4.3455, instead of 4.342. Piston are all slightly undersize (3.438 - 3.440). the other bores are all slightly over without any hone at all (from about 4.343 - 4.344). The pistons are sealed power hypereutectics, compression is around 9.5, no more. The engine may have seen 2000 miles since rebuild, did it wear that much or was my machinist overzealous.The pistons are sealed power hypereutectics, compression is around 9.5. Tach will never see the dark side of 6000 rpm, limiter at 5600. Anyway, thanks for looking this over, any help would be sincerly appreciated. other comments are welcome, (I know why would anybody build a buick.. It was there).