Originally Posted by
eksz
1. Try soaking with PB Blaster.
2. Heat and cold cycles (torch and ice or dry ice) and shock (use a punch and hammer and smack the bolt as hard as you can) should help losen up some of the rust, ect that has it fused. I'd be cautious about heating bolt red hot for fear of posibily damaging the end of the crank.
3. Repeat steps one and two periodically.
4. Take a file to file the bolt head to create two oposing flat surfaces that you can grab with a wrench (not pliers or vice grips).
5. Drill out the center of the bolt taking care not to run into the threads of the crank. Unfortunately in my experience most of the bolt extractors tools work at best only 50% of the time and if they break off inside the bolt you are in a worse situation as the extractors themselves are usally case hardened and near impossible to drill out..
6. Some machine shop have a tool that they can use to burn the broken stud out. It was like an arch welder but was made especially to destroy bolts stuck in fly wheels, blocks, ect. I had to do this several years ago on a flywheel.
7. Worse case, cut, dremel or file the bolt head off. This will leave you a stub of the bolt sticking out that you work on. If nothing else, the stub of the bolt sticking out can act as a pin (dowel) for alignment and you'll still have the other 6 other bolts to secure it.
8. While I have never tried welding another nut on top of the rounded off one andthen ging aftr it with an impact gun. Heating a socket and smacking it onto the rounded bolt, also sounds like it could work. I'd probably try and shape the bolt head with a file so the socket was a closer fit.