remove exhaust manifold bolts

Cut off the stud even with the head. Put a bubble of weld back on the stud with a tig welder not a mig. this will heat the stud/bolt threads. Now tig weld a nut to the bubble you put on. cool it quickly with air and they will spin right out.

You must cut them flush when you do the weld trick. and you must use a tig welder. a mig weld is brittle and will break. Also the tig will put more heat in the bolt/stud. We do this all the time on motors in the vehicle or with the head off. This method will not work if there was a he-la coil installed in aluminum.