My wife's 86 745T had several broken exhaust studs. I was able to drill and remove all broken studs but one. In order to remove it, I pulled the head and put it in the kitchen oven, at 225 degrees F., for about 45 minutes. When I pulled the head out, it was at about normal operating temperature. The broken stud came out with torque that would not remove it at room temperature. The thermal coefficient of expansion for aluminum is very close to twice that for steel. Now the kitchen smells like an automotive machine shop. It is a good thing that Thanksgiving was three days ago, or I would be out on the street. My wife would never let me fix my car this way, only hers. If you choose to use this method, I don't recommend locally heating the head, as you might warp it.