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.
1 Have a drill and bit on hand to drill out any broken bolts and a re-threading bit. 2  Never try to remove the exhaust manifold bolts on a hot engine, the extreme temperatures of the exhaust manifold can cause the PB Blaster to catch fire when applied; always allow the engine to completely cool before beginning work.f you do not have threads from the bolt exposed, but a flat bolt head, use a stud puller instead of a box wrench. If you are using a stud puller, skip the rest of the steps and begin working the stud puller in a counter-clockwise fashion to loosen the bolt.