Actually, cast iron has been welded successfully for longer than any of us have been alive, but it must be done prpoerly- - - -there are simply no shortcuts. It's done with a reverse-polarity DC stick welder and nickel-alloy rod, after preheating the metal. Weld about 1/2" at a time, and peen the weld bead for a few minutes with the pointy end of a slag hammer to stress-relieve the bead. preheat again, weld, peen, etc. until the entire crack is covered. Before welding, the ends of the crack need to be stop-drilled with a small drill bit to keep the crack from spreading. You still might be able to salvage that block by doing the job corrctly- - - -after grinding all the MIG material out.
Jerry
