Posted by JBizal on Tuesday, October 23, 2007 at 21:43:07 :
In Reply to: Repairing a cracked exhaust manifold posted by David Sherman on Tuesday, October 23, 2007 at 00:35:21 :
You can braze the cast iron back together with brass material. The problem will occur when you start thermal cycling the manifold after you reinstall it. It does not do well with the high heat and then cooling off again. The preferred method of welding manifolds is with a nickel powdered metal alloy and a special torch. Using nickel stick electodes really don't work well since the free carbon in the manifold has been baked out and the heat effected zone will 90% of time crack right next to the weld. Pre heating is an absolute must. You must bring the entire manifold up to at least 700 degrees and more importantly, slow cool it. Bury it in a heat blanket, or vermiculite. Before I got into the truck business full time, I spent almost 20 years in the specialty metals and welding business.
John
Follow Ups: