Hi,
A friend of mine, who's father was a blacksmith showed me a cool trick for exhaust manifolds, especially ones subjected to very high exhaust temps.
Someone had a cracked one off of a motor home. They taken it to several welding shops to have it welded, but the welds always cracked. He explained that this was due to the repeated very high heating and cooling cycles changing the chemical composition of the cast iron, basically making very brittle.
His solution was to torch weld it with a cast rod (looks kinda like key stock) with a solid copper 12 gage wire wrapped around the od of the rod. He explained that the copper added ductility to the base metal. His repair was was great, and did not re-crack.
I have used this method a few times myself (with a cast flux as he did as well) and it has always worked well.
I'm not sure of yours or a coating or not, but I just thought Id add this. Everyone here as probably seen or done this already.
Jeff
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