These little beggars have a reputation for seizing in place. If they are all cooperative, yes you can remove them without pulling the engine. If the heads are rounded or if a stud breaks off you are looking at pulling the engine. I would suggest some heat from a propane torch and a shot of Release-All or WD 40. You can also put a second nut onto the stud and tighten it to the first nut. Heat the metal where the stud goes into the head, add a shot of Release-All and then back the inner nut against the second one and hope that the whole stud unscrews from the head. I have gone 3 for 4 removing these studs from VW heads. When you put the new nuts on, give the stud a good covering of Never Seize compound. Don't you wish the earlier owner had done this? Good luck with the project. Dan (MY72BUG) in Goderich
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.