The top ring was broke, seen some egts alright, but still, this piston was a wimp....and has fishy crack. You can see this crack that kind of follows a 45 degree to the steel ring land. The other 5 look like new.

Clearance, Clearance, Clearance

 

head gasket? cant see the position of the pin? but the stamp in still their

 

What were you running when that happened?

 

Was running the Tst when the initial damage, or failure occured, But seemed harmless, a bit of blow-by, I knew one cylinder had some issues. Wanted to try a smarty and on the first day with some timing finished that wimp off.

Sure liked the Smarty the bit I ran it, liked it more than the Tst, and way cooler egts.

 

Throw that runt of the litter in the scrap bin. Natural selection, only the strong survive! It has STD's anyway, I could see it.

Which hole was it? The rearmost cylinders see the highest EGT's and that piston was in meltdown. The damage was on the exhaust side so I am going with too high EGT with a Friday piston. Good thing you caught it before it got worse. You know the drill, check the valves while the head is out and reassemble.