Of all the jobs I have done on my Model A, the one I hate the most is re-torquing the head. I have had that experience of having a torque wrench go from 52 ft. lbs. down to 25 ft. lbs.. It was on a rebuilt engine in which I was installing the cylinder head. I should have had the rebuilder install the head! In my case, the studs were a new set and it broke off flush with the block. I remember going back into the house and I know I had "wet eyes" I was so upset. I called a club member and he game over with a set of small cold chisels, one was only 1/8 in. wide. In ten minutes with light tapping on the circumference of the broken stud he had it backed out of the block. I couldn't believe it was so easy.
I have also put in helicoils and managed to tap the hole badly (the new stud was not perfectly vertical). Now what?? Before I put the cylinder head back on, I looked at the bad stud, saw which direction the stud was leaning and took a round file to the top of the head and opened the hole slightly to relieve the pressure between the head and the stud. I installed the cylinder head without the bad stud. After the head was lightly fastened in place with other studs and nuts, I ground a slight taper on the end of the stud so that it would engage the hole in the block better, I applied Never-seize to the threads and dropped the stud down in the hole. Then, with two thin nuts I screwed the stud down into the block. It was amazing, the stud when in with moderate effort and was torqued in place. After 5000 miles, it is still going strong. You do what you have to do. Ed