What happen

[jed]

This is a 6.0L LS. All of the other cylinders are good. As can be seen the 2nd ring land was torched at the ring gap.
I've seen torched Pistons but not like this.
Any thoughts

[prairiehotrodder]

how many miles were on it since it was put together ? Did it butt-up ? Not enough gap ?

[jed]

Less than 3K. I don't think the rings butted. The picture of the piston top shows there was no detonation.
But I think detonation was what caused the torching of the ring land.

[Darin D Morgan]

Now that is a cool one! I see destruction in just about every flavor imaginable and that one is new to me.
It almost looks like it had 20-30 degrees to much timing in that hole but why it didn't nip the ring land first is a mystery to me.

I think all your going to get out of this is a bunch of speculation but then again, you dont want to go back together and have the same thing happen.
Did it get only one hole or are other holes exhibiting signs?

[Racer71]

Is it me or that a lot of scuffage or galling on the skirt? I assume it be from the ring issue. Have you measured the bores with a torque plate installed post tear down?

[jed]

Wow Darin didn't expect a response from you and I have to say thanks for responding. I used to do a lot of turbo charged imports high boost stuff in the range of 40/50lb and this is a new one for me. That's why I posted it.
No to the torque plate and yes to the to the scuffing. I will do more checking Monday when I am back at work.

[econo racer]

I would put the rings back in and check the gap. Also that piston looks like it was way tight. Diamond is good stuff too. Sorry to see this

[ClassAct]

If that is the "backside" (not the thrust side) of the piston, I've seen this happen when the spark plug is too hot. You don't see any signs of detonation or anything weird. You just see the backside scuffed.

[Roundybout]

That almost looks like pre-ignition damage. Can you have pre-ignition without detonation? Is this an injected engine? Something wasn’t happy in that cylinder causing a lot of heat. What’s the underside of that piston look like?

[BILL-C]

Put ring back in bore and measure end gap. If gap is way too big it might cause a hot spot from the larger volume of hot blow by and fuel burning that collected in accumulator groove. Also a good idea to compare the free gap on that top ring to a good one to check for radial tension loss from excess heat.

[rfoll]

Is it just me or do I see a small piece of piston ring buried sideways in the bottom of the ring land? If it is it would tend to indicate ring butting.

[af2]

This is a 6.0L LS. All of the other cylinders are good. As can be seen the 2nd ring land was torched at the ring gap.
I've seen torched Pistons but not like this.
Any thoughts

It would be nice to see the ends of the ring. Shiny = butting

[LoganD]

Was this turbocharged or boosted in some way? From a purely visual standpoint it looks like the piston got too hot and the aluminum annealed, ruining the forging. As some have said, that scuffing looks absurd, but more importantly it's got surface pitting as if the surface hardness was very low. Some piston oil squirters would solve that.

If it wasn't turbocharged or boosted then it appears piston to wall clearance was wrong as someone suggested, which would also overheat the piston.

[Orr89rocz]

Fuel injected? Ls coils?
Curious if that cyl injector was clogged or not delivering fuel and it ran abit leaner to get hot? How did the plug look?
Also what was the dwell on the coils? Some coils have autofired at high dwells before

[cjperformance]

File fit rings with burs/chipping left on the end edge. Picks up some piston material and sticks the ring in the groove holding the gap area away from the bore, torched piston.