My 1955 Plymouth has a hole/crack in the exhaust manifold. Can I use JB Weld to repair, or will the heat of the manifold be too much for JB Weld?
It will be way too much heat for the JB Weld, but there are other special glues that will do the job. One I got from Advanced Auto, and it is meant for just such an application.
I don't think regular JB Weld would be a good choice.
JB Weld High Heat or JB Weld Extreme Heat might be good for the job.
The exhaust manifold will easily hit 1200°F and higher. Base your selection of "glue" on it reaching 1800°F.
The JB Weld Extreme may hold up.
There are high heat ceramic-filled epoxies available from McMaster-Carr, that withstand temperatures in excess of 2,000 degrees F. Go to www.mcmaster.com and type "ceramic epoxy" in the search box in the upper left hand corner. The adhesive for cast iron, stainless steel and steel comes in 2 sizes. 8 oz. for $55.89 and 16 oz. for $104.89. It is a one part pyro-putty. Good luck. Jim Patrick