+1 on mapp gas, gets hotter than propane. Heat the stud low, but be careful not to melt the the cases, spray it a couple times with wd or pb blaster, (do this outside if you can because of the smoke)it shocks it plus lubes it, heat it back up and then use either the bent over method or double nut with a impact gun. If you get a real stubborn one you can rap the end of the stud with a ball peen hammer while it's hot. Patience is the key.