I'd go with LUCK! Last one of those I saw, the piston was in a million pieces laying in the oil pan and had a 2" hole punched through the cylinder sleeve where the rod shoved something through it. Everything was toast but we actually got the core charge back and that was a shocker.
Valve keeper fell off the stem, it was a reman engine and I think the builder used the wrong keeper(s) or didn't get that one on right? It had been in the boat for years. Stainless steel valves.