It sounds like that guy better stick to machining, because he's not going to make it as a cast iron welder. Even if the repair was made with nickel rod and an arc welder, his procedure is wrong. Yes, it's necessary to preheat, but not even close to red. Weld about 1/2", then peen the weld with the pointy end of a slag hammer for several minutes. Heat again, and weld another 1/2". Peen again. Continue until the crack is covered, and hope it doesn't leak where the welds overlap. Brass is a much better choice, but it takes a skillful welder to do it right. Get the area all around the crack CLEAN, (several minutes with a wire brush in a die grinder) and groove the crack deep enough for the brass to build up a good bead before it reaches the surface level of the rest of the block. A good brass-to-cast iron joint will be smooth where the two metals blend together, not piled up like pigeon poop on a windshield!
Jerry
