This is the first time I've had something like this happen. When the piston came out, the ring gap was right there where the ring land broke. No signs of pock marks from detonation on the top of the piston either. I'm not saying it didn't happen, but I didn't hear it happen. There was one time that I went WOT with the stereo cranked though, the day before I heard the knocking. By the time the engine was out & apart, the piece of piston had blown out the exhaust. The spark plug gap was also closed up a bit. Compression test was 175-185 on all cylinders.

Tim, good idea on checking GM's specs on those engines. I'll dig around in Mitchell later today and see if I can find anything. GM's spec for the L33 is something like .009-.0196".

I'm gonna borrow a bore mic, verify the block, then I'll probably just buy one new piston from GM, regap the rings, and slap her back together.

 

I would put the ring on a flat surface and see if it is flush with the surface. That, along with small abrasive marks on the ring ends will tell you if it was too little gap. Its often hard to see, but should be noticeable if you compare it with a good piston ring with a magnifying glass. When my #3 cylinder took a **** on the stock 6.0, the ring was all bowed up and the ends were scratched up.

Pictures of the ring ends aren't good enough to really show anything, but here's how the ring looked:

 

I already checked the ring for flat. Looked okay to me. I'll look at the ring ends more closely tomorrow.

 

Might have been detonation then

 

Sorry to hear that Roger. Is there a scratch in the cylinder wall? I have seen them touch, and the tip of the ring sort of smooshes over, and leaves a scratch straight up and down the cylinder wall. Was there any damage to the heads?

 

I have read that the stock ring gap is fine for even boosted apps. Sucks yours took a crap.

 

Sucks Roger, sorry to hear that. Hope you get it all back together and running like a raped ape again shortly.

 

The one pic has a # 1 piston on it,was that the hole it came from? Usually its # 7 that blows land first,my buddys denai 6.0s same thing happend #7.It beat up the head a little and the bore was fine,we tossed in a new stock piston and the stock heads went back on.Ran perfect,went back stock

 

Sorry about your luck, Roger. I was kinda wondering how long those hypereutectic pistons would hold out running like that. Good luck on the repair and post us up a vid when she's fixed.

 

My builder recommends .0065-.007/inch of bore at a minimum in a boosted application, for what it's worth. I think stock on the 6.0s is around .015 total ring gap. I also lost one of the front pistons as opposed to the normal back two pistons except mine broke the oil ringland not the top ringland. I don't have a very high opinion of the stock pistons.

As far as reusing the stock rod bolts- I thought they were torque-to-yield like the head bolts.