Hillsborough County schools get out May 25 for the summer break. ChaCha on! 7 years ago
Â· just now. Report Abuse. A cast iron manifold will expand and contract, the JB Weld will not. I think JB Weld is fantastic stuff (have some as we speak) but not for a cracked exhaust manifold.You can always check out their website: http://jbweld.net/index.php I only have experienced JB with cast though, if your manifold is another material you may get lucky.ource(s): Q: Will J-B Weld work on an automotive exhaust? A: Because of the extreme temperatures of exhaust systems, we do not recommend J-B Weld for use on exhaust manifolds and catalytic converters.
The exhaust is average of 500 degrees. The hottest part at the converter. If you are repairing the exhaust pipe or muffler, JB weld will work but will only be a temp fix. With The constant heat and cool down of your exhaust I dont know how long it will last, but low heat shouldnt be a problem with this product unless your using it on the converter. kellyglockman Â· 9 years ago. Thumbs up.