"Been there done that" Try the back out bit as described earlier. That is the best chance to remove the broken bolt. I am not sure if you are working on a big block, but my work was done on a 440. I also agree with an earlier statement that suggested original bolts or grade 8 bolts. Do not get cheap bolts. You can buy a set of good ones on ebay:
- Item: 401171034203 I would not get the 12 pt bolts
Now, if you accidentally booger up the threads, try to repair them with an appropriate size tap. If that gives you too loose of a bolt, or the threads start to strip, you can always drill out the threads with the bit that the coil calls for, tap it for over sized thread coil that has the same ID as the original bolt. These coils are stainless steel and work really well. I also agree with a previous poster, don't remove the pan unless there was a leak previous to removing the manifold. Finally, use your torque wrench beyond snug. I believe the book calls for 50 ft. lbs, check it in your manual. I would stop at 35 and see what you have. You can torque them up while you watch your vac gauge but if you are maxed out on vac I'd just leave them at 35-40 ft. lbs. You run the chance of stripping the threads on old used threads, especially if you torqued the previous bolts to the point of popping off the heads.
I hope this helps. I hope you do not have to go as far as using a coil, but if you do, don't freak out over it, it is not that big of an ordeal. Oh, one more thing, if you do use a coil, make sure that you follow the instructions on how far to screw the coil in. Also, someone mentioned bottoming out of the bolt. My head on the 440 (915) has threaded hole through the head. If yours is that way, make sure not to get shavings down in the head.
