Heat the stud red hot with an oxy-acetylene torch (use neutral or carburizing flame) immediately adjacent to the gasket surface. Tap the end of the stud with a hammer. Use a light blow. Let it cool to room temperature. This process causes the stud threads to break loose and shrink. You should be able to grab it with a ViceGrip plier (or two). Apply torque and simultaneously tap the end of the stud with a hammer. Use a moderate blow. You'll probably need a helper.
DO NOT attempt to turn the stud until it cools completely, or you *will* snap it off!
Heating expands the stud, which is constrained by the surrounding casting. The softened threads deform and the stud permanantly elongates. As it cools the threads shrink in diameter. Tapping with a hammer when hot helps the threads deform, and tapping when cold applies vibration to break the thread loose (similar to an impact wrench). Heating and slow cooling the stud also changes the microstructure of the metal such that its softer and weaker.
Be patient! Let it cool completely!
If it didn't loosen or snap off, you can try heating the casting around the stud, but not the stud itself. This expands the casting to a larger diameter, and loosens its grip on the stud. Use the same ViceGrip and hammer procedure after the casting is warm. You can also cool the stud with an ice cube, just don't cool the casting. If you heat the casting, you must turn the stud as soon as the casting is hot. Do Not Delay! If you delay, wait for the parts to cool to room temperature and start over.
These heating methods will successfully loosen 80-90% of "frozen" threaded fasteners without damaging the part. I use the same methods to loosen rusted brake bleeders (haven't broken one in over 20 years). With brake bleeders though you *must* use a 6-point box wrench or socket. A 12-point tool will round off the flats and make removal much more difficult.
As for the torch, I recommend using a cutting tip, but do not hit the cutting oxygen trigger. The six preheat flames will quickly heat the part. After you use these methods a few times it will become second nature and you'll get a feel for how hot, how long, how much torque and how much hammer blow is required The ViceGrip needs to have sharp teeth on the jaws. Buy a new one if necessary. I prefer the curved jaw of a #10CR or #10WR. Clamp it on as tight as you can, in the deepest part of the jaw.
Ken
