JB Weld....

One time in the middle of Kansas at a meat processing plant, we had to repair an old Vilter piston-type ammonia compressor that had a stripped out head bolt. The head was a "flat-head" type like on an old Ford flat-head V8. The threads were stripped out in the block. This hole was a 15/16" hole, wrench size was 1 1/4".

We completely drilled out all of the old threads, filled the hole with JB Weld, re-drilled the hole, tapped in the new threads, and re-installed and torqued the head.

That old compressor started right up, held the pressure, and worked just fine.