Broken bolt removal

Not sure it this is the right section of the forum for this question. But,I have removed bolts broken off before by holding a nut over what was left of the bolt and arc welding the nut to it. They usually would come out fairly easily but not always. My question has to do with mig welding or arc welding on a full assembled motor. Would welding the nut to the bolt also arc through various engine parts, such as crank to bearings, piston to cylinder.