Originally Posted by tresi
You have machine the stud boss in order to install a shouldered stud and guide plates. I couldn't even guess how many people have pulled the loose stud, tapped the hole and put in a non shouldered stud and went down the road without pulling the heads. It's not the prefered way but if care is taken to keep the tap straight and get all chips out it can be done. Be sure use some sort of thread lock on the end of the stud that will go into the head.
There's actually a very economical and easy to use tool available from summit that is used to pull the stud and then, using the stud beside it, guides the tap so it goes in straight. Rockere arm stud removal/tap guide tool