Ended up with a catastrophic failure on an 8.3 that was in our motorhome. We actually melted the #6 piston.
I was headed up a hill with no shoulder when I saw a big cloud of smoke. Pulled over as soon as I could and waited for things to cool down. Ended up getting towed. Pulled the head and the last piston had melted. Hole through to the rod and aluminum sucked up into the head. Total mess. None of the others showed any similar wear. My guess is it has to do with an injector, but really no idea.

Thoughts?

This is an older 12 valve mechanical injected engine.

 

Sounds like an injector. Do you have a pyrometer on it?

 

unfortunately not.

 

It may have had an injector crack and over fuel the cylinder. The # 6 hole always run hotter than all the other cylinders. How scored up were the cylinder walls?

 

Not as bad as you might think, given that the piston was melted. Bad enough that I'd change the liner, but most of the issue that's obvious is the metal transfer from piston to cylinder wall as the piston went away. Interestingly, the injector was nearly new. It had less then 2500 miles on it.