JB Weld is iffy. It might hold up it you keep the engine rich and cool. I've also seen it fail in 30 seconds.
Conley Weld is better.
DevCon High Temp Epoxy is will work for sure. Unfortuately, it doesn't seem to be on the market anymore. Marvin Denny was kind enough to give me what he had left. I should have stocked up in '74. That stuff never fails, regardless of temp.