Well, I think you are relatively screwed on this one. Sorry, but it just is the way it is. <img src="/forums/images/graemlins/smile.gif" alt="" />

The Al threads should have pulled a long time before that plug snapped. So...you either have a tremendous amount of galvanic corrosion between the head and the plug, or it is really really cross-threaded. The other option is that the threads have pulled and it is now wedged in there nice and tight.

In the end, you are probably going to have to pull the head. Sean's suggestion of penetrating oil, heat and an easy out is good, but you are going to knock the electrode and the remaining porcelain into the cylinder and I think that plug is going to need more than heat and some massaging to come out.

The dude on Pirate had a few things going for him: 1) The engine blew all of the porcelain out. 2) He probably had iron heads.

With the head off, you can take it to a machine shop and have them fix it correctly. I am going to bet that you will need a heli-coil. You'll also have the chance to inspect the other spark plug holes and see if they need attention too.