When piston collapses it will eventually effect ring seal. I’ll explain it the best I can pistons all pistons are tapered. When they collapse the tapered goes way. If that block has a ridge. Most likely it was caused by mileage and or a collapse piston or both. Looking at those piston and ridge I would definitely check to see how much of a over bore would be need…..030 over bore or .060. Most with that king of ridge need a .060 over bore. Running a Dial bore gauge though will tell you how much it needs.
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