I bought a rebuilt 455. It is supposed to be a stock rebuild. I opened it up to see what I really had and saw that the main and rod bearings were standard, so I took off a head and found big valves and low compression pistons. The thing I don't know is what bore or overbore the pistons are at. I thought I would see 030 or 040 or something similar on the pistons but all I see is the letter C on three pistons and a B on the fourth. The pistons have a really deep dish. That is why I said they were lo-comp pistons. If anybody can help with those letter markings I would really appreciate it. Thanks in advance.

 

Those are factory tolerance band stamps. They should correspond to identical characters stamped into the head gasket surface of the block adjacent (more or less) to each cylinder bore. I was not aware that aftermarket pistons carried these markings, so, unless someone here knows better than I, I would suggest that these sound like the original pistons (and therefore bore). Pictures would help.



This chart is from 1972 - I am not certain whether the details are the same for all years or not (would have to review each CSM...).

- Eric