RE: Muffler threads are stripped; how hot does an engine get
I agree thats its probably best to just start with a new muffler.
Personally I dont like to permanently glue the muffler. I think if you use teflon tape or rtv the mufflers stay on fine and you can remove and reposition when necessary. I just make sure that the threads on the header go as far as possible into the muffler and the engine.