remove exhaust manifold bolts

If the stud is sticking out before it's broken off hit the top of the stud with a hammer several times then heat the area around the stud but not the stud it self. You need the heat in the area around the stud to make sure it expands then use parifin wax and touch it to the stud it will wick down around the threads of the stud once it would cool down a stud extractor will turn the out of the head with min effort. I learned this from a Mack Truck Tech and have used it hundreds of times without much trouble