Somebody had a good trick. (need to be good with a Wire Feed Welder)
Weld a flat washer that has a 1/2" center hole to what is left to that stud in the head. Then take and weld a 3/4" nut to that washer so you can get a socket on it and spin it out.
Welding wont stick to the cast iron head very well, so it should spin out. Plan B if all else fails is helicoil back to stock size stud.
