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.
Now if it is a crack, I would take a small grinder and just lean up the area around the crack and then try the JB WELD. I have used it and it worked and I have used it and it hasn't worked. It's a couple of bucks you can throw at the problem.The above suggestions are fine but I always try a cheap way first.ow if it is a crack, I would take a small grinder and just lean up the area around the crack and then try the JB WELD. I have used it and it worked and I have used it and it hasn't worked. It's a couple of bucks you can throw at the problem.