that crack off has happened to me several times with my arc welder with the propper rod. i think i may get a little impatient and try too long of a bead before i stop. who knows about mig welding it, i have never tried. with enough heat for penetration a crack would be easy to happen. i do use dc rev pol on my old hobart too. like i said in my earlier post it's a toss up if it works. i'm sure a pro welder would have a higher sucess rate. the key prob is the short welds and peening like jerry suggested. i don't know, i have just had so much better luck with brazing, i don't know if i will ever try it again. i still have some nickel rod. when i found a crack on the head of my flathead hudson, i just jb welded it and it has held up good so far. at $100 a pop for a head gasket i din't want to remove it again to try the brazing.
