[b-man]

When I was having my 421 block bored .031” oversize for some 4.125 pistons I had purchased (stock bore is 4.09375) it came to our attention that someone had ruined the upper 3/8” of the bore using a ridge reamer sometime in the past while doing a ring job on the stock pistons.

I sold the 4.125” pistons and bought a set of 4.135” pistons which was the smallest size the bores would clean up at. I guess buying the pistons beforehand was a mistake, I was trying to expedite the process by purchasing what I thought would be the right size. However they would have been right if someone hadn’t screwed up by getting heavy handed using a ridge reamer.

A ridge reamer was commonly used in the past when someone wanted to do an economy rebuild keeping the old pistons. If you’re doing a proper rebuild with new pistons just skip the ridge reamer nonsense and get those old junk pistons out of there, who really cares if you break some rings or damage pistons that are already destined for the scrap bin.