Whaaa? Cut it flush after you dick it even more with vice grips or a pipewrench, center punch it and start drilling small to big until you get to threads. Use punch to pry away from threads and drive remains into block if its not a blind hole (end ones are open) chase or tap and put new brass stud in with sealer. Buddy had to EDM one out at aerospace job from a 383 head. That freeze stuff is cool, heard you can freeze the bolt and shatter it with a hammer, never seen it happen but heard it worked. Also an Acetylene torch to heat bolt and a blast of Oxygen at the last minute to blast it out, that was from this board somewhere. Them are some soft studs.