Cracked exhaust manifold

manifolds are funny to weld. im not aying impossible, but all the heat cycles they go through really changes the cast iron. i like to braze them. for my 1931 essex i had a piece that was completely missing from my manifold where the pipe bolted up it has a 3 bolt flange. once i cleaned it i could see it was already welded with nickle and there were a ton of stress cracks in it. i ground it all out threw it in my bbq at 500, heated the area to be brazed to a dull red and built the entire area up out of braze with a cool flame, nice and slow. i used a ton of braze i didnt really have any choices as the manifold is pretty much non existent. it held up great. i do not like the nickle rod. there are some old timers out ther ethat weld cast iron with cast iron. there is no rod available, they use things like broken bath tubs and piston rings for filler with flux, preheat the **** out of the part to where all of the expanding is done and gas weld it up, heating the entire part until welding is complete. then slowly walking the temp back down. i nthe end you have a part that is welded with machinable cast iron. it has the same properties through out. the last thing you ever want to do with cast iron is mig it. you wind up with a very hard brittle weld that attracts al lof the carbon fro mthe surroundign area.