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.
Worse, if the. rectification job is botched the engine may need some serious repair work. If exhaust manifold studs do. need replacement they can be replaced in an idiot proof fashion providing the owner will expend a little of. the coloured paper from his or her wallet. Trying to save pennies, cents or whatever makes holes in your. pocket, will not help in this situation.