"Leo Lichtman" wrote in message
...

"David Billington" wrote: (clip) If the screw head can be ground off and
the muffler removed then
careful heating of the screw adjacent to the block may get enough heat
in there to help loosen it, (clip)
^^^^^^^^^^^^^^^^^^^
If you can grind the head off. that may release enough tension on the bolt
to let you turn it with vise grips.

The last resort method I have used, which generally works is:

Drill carefully into the center of the bolt. Correct centering errors by
leaning the pistol drill as necessary. Start with a small drill bit, and
then increase the size in steps. You will reach a diameter where there is
very slight contact between the drill and the ID of the threaded hole. At
this point you can probably pull it out like a spring with a pair of
needle nose, or clean it out with a tap. If your drilled hole is slightly
off center, then pulling it out like a spring won't happen, but you may be
able to pick it out or tap it out.

This does not require any heat.

As a last-ditch method, I'm with you on drilling them out. I've broken off a
few exhaust-manifold and muffler-clamp bolts with my hammer-driven impact
driver. And those bolts are usually mush after a few years of cycling in all
that heat. I've wound up drilling out a couple of them, on a Honda
motorcycle and on a Volkswagen, with the method you describe.

--
Ed Huntress