Torching cylinder head

Pulled the motor apart today. Zero damage to the piston, spark plug or bearing. There is a small channel, looks like a burn track, inside the hoop that runs about 30 degrees from the main damage. No other signs of heat.

 

Could this be a mag grounding issue and the "channel" is an arc mark?

Just throwing it out there...

 

I have a 10 gauge wire running from the ground post on the coil to the front side of each cylinder head. The torch burned through it both times. Also a ground from the coil to the chassis.

Also, we noticed the middle intake nut kept backing itself off.

 

Check your studs for stretch. I had one to do this, reused the studs in that corner, and it happened again. You could see marks on the heat gasket that gave the impression the head was basically bouncing on the block.

 

Could you feel any difference versus the others when torqueing that particular one down? Could you see any difference in that stud? Just curious.

 

Have the deck surfaces been checked for flatness?