I have the stock lines with stock pump intank and walbro 255 inline. I wouldve thought if af ratio was good then it had enough? I havent pulled it apart to see if it did the same thing or scorched a piston yet though. I wouldnt think with them gapped at .030 that they would touch though.

 

What did the pistons looked like when you pulled them out?

 

Here's your fix. Go to salvage lot. Find another 6l with good compression and drop it in. If the tune is spot on and is not leaning out, dropping fuel pressure, and not knocking then I would say maybe the motor is permatley hurt from the first mishap. 11.7AFR is alright on race gas,methanol or e85. But on pump gas thats pushing it. I tune mine 11.5 on e85.

 

If i put another motor in it im calling it quits and putting a stock 5.3 back in it. I just built this motor in may and i dont make enough money to just go buy one to replace.

Spoolin, the pistons look just fine when i pull them. No signs of detonation whatsoever.

 

What about carbon build-up? How bout the back of them, were they discolored in the back?

 

They dont have much carbon build up at all. And the back are clean as new. Keep in mind this motor might have 2500 miles on it.

 

Here are a few pics of the last piston that got busted due to ring gap.

 

i would richen it up alil, 11.7 is alil lean i think

 

Did you check your bore size in a few different places? Top-Middle-Bottom, 12-6-3-9 o'clock positions? If that cylinder heated up more than the others from a coolant blockage or lack of cooling period, the cylinder can distort to an egg shape and or taper larger to smaller from top to bottom.
The piston looked like it was going up when the ring lands broke. That makes me think that there is a problem with machining or trueness on that cylinder.
I am not an engine builder but have built engines and have a general knowledge of them so this is just some questions and observations I have made.
Let me know if you find something out!

 

Ive already pulled motor apart and put back together. What i plan on doing is putting an egt probe in both number 7 and 8 to verify the differences between the two.