Never run my junk 7.4 lx mpi's under 1/4 tank, nor any other vehicle.

I've had the same failure on some old blow thru carbed turbo motors years ago ( till I got them dialed in). Happens quickly and cuts a perfect groove. Lean motors usually make more power until... Good luck.

I/2 an inch or more. It is not entirely smooth, it almost looks like it let looses and the heat took over. You can see casting like a break with the surface starting to smooth over like melting. It certainly could be burnt but the block is perfect including the deck and that is the only damaged. we even pulled the valves and they are perfect. Even the adjacent Intake. I get the Inconel not burning.

yes, now that i think about it why didnt the block burn up too? i could see if the heads were aluminum they would go first.

this is why i went with big (557) cube n.a. engines. big , fat , and lazy engines that make good power without trying hard. those blower motors require everything just right and you know fuel quality can be an issue.

I had the same failure in my old Merc 420 NA. Brought the head to the machine shop. They welded it up, machined it smooth, put a straight edge on the block, new gasket and it was good to go. The block doesn't get torched because the block has cooling. As stated earlier, the head has a hot spot there.

This^^ block is cooled that's not a casting issue, any casting issue would surface right away, lean issues melt thigs very fast, seconds...

It was, maybe 20 seconds.

All it takes..

If a piece had broken off you would have damage to the head and cylinder from the piece ratling around in there.
You ran lean.

yes you would think that chuck would cause damage on the way out. that is amazing to me that it cut right through like a torch. learn something everyday.