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Paul, a windy reply: I am much better with oxy-acetylene than stick, so I used brazing rod #526fc. I bought two pounds, but only used one stick to complete this job! The manifold was in very poor condition. I was prepared to throw it away and use this as a learning exercise. First I wirebrushed the manifold as clean as it would get. This produced a hole in the casting as well as the broken end of the exhaust section. Still, nothing to lose so I kept going. I used the bench grinder to grind off the edge all around the broken piece, producing a place for a bead to form. Then, I clamped the broken piece into place and put the whole thing into a vice. Next, I used the torch on very low heat and heated the entire manifold to 315 degrees (Just kidding. Got it hot.) Then, I welded, without regard to anything special. The rod wetted the metal pretty easy, particularly if I rubbed extra flux on it first. Fixed the break, fixed the hole. When done, I put the torch back onto low heat and kept the entire manifold hot for five minutes or so, lowering the heat gradually. Then, I turned off the fan I was using in the shop for exhaust and let it cool as slowly as possible. I did not follow Steve's recommendation to slow cooling further by immersing into a sand bath. Lastly, not welding related, I painted the manifold with rust converter, then painted with hi temp gray. Looks good! I'll toss a pic to you tonight and brag about my handiwork.
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