In trying to remove the header pipe the metal flange that goes over the two studs will not come off. It looks like one of the studs is bent outward and even though the flange is loose it can only move out over the studs about 3/16 inch. Any ideas on how this got bent, and how I can straghten it. It's going to be hard to get to with the pipe in place.

Never mind. It was the lower stud that was bent down. I was lucky that a pry bar between the stud (with nut on) and the engine case gave enough leverage to bend the stud back up. Still can't imagine how someone managed to bend the lower stud down. Looks like any empact on a rock or log would have bent something up.

Sounds like a good time to replace that stud.