Date registered: May 2013
Vehicle: 1961 190SL
Location: Northern California, USA
Mentioned: 0 Post(s)
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"According to one welder, who specializes in cast iron welding, the entire manifold will have to be heated up. The additonal risk noted was that upon heating the entire manifold can crumble."
As I said in my prior post I'm a geologist, not a welder. But, I've always been very interested in welding and while a graduate student in geology in the 1960's I took a welding class. About 40 years later I bought a tig machine and I'd totally forgotten the tig technique so I took the welding class again to relearn tig.
From that I know that when any large piece of cast iron is going to be welded it has to be preheated and postcooled to prevent cracks from concentrations of heat. Properly equipped welding shops have ovens for that purpose. Hobby welders accomplish the same thing by preheating the item on a BBQ, welding it, then cooling it slowly on the BBQ.
Uneven heating of iron pretty much guarantees cracks from forming during the cool down after welding.
Competent welding shops not only repair exhaust manifolds but even engine blocks and cylinder heads.