...unless you have press-in studs, as some of the small valve, lower performance heads do. In this case, depending on how far down it broke, there is a proccedure in the Pontiac Service Manual for removing studs. If it is broken off too far down, you might have to drill into it, tap it for a 1/4-20 screw, and then thread a screw into it to help in pulling it. This might best be left to a competent machine shop. Last would be to take it to an EDM house that specializes in broken tap removal.