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.
Step 4 - Block Heating. If you canât loosen the bolt inside the engine block, then loosen the engine block around the bolt. Use a hand held torch to get the engine block around the exhaust manifold stud as hot as possible. The stud casing will expand with the heat, giving a little wiggle room for the bolt.ust and corrosion can also fuse the exhaust manifold studs to the engine block of your older vehicle. Whether itâs to replace the manifold itself or to get at other parts inside your engine, off the bolts must come. When your exhaust manifold studs are stuck, try these tricks to get them off.