Originally Posted by aklim

Yes. However because of the nature of the hole (too tight) you cannot get at that area to weld material to it. Since we drilled to the point of the bevel, it wasn't sealing when we got the plug screwed in. The machine shop showed me the other holes. Between the bevel and the thread area, there was little or no carbon. Therefore, the conclusion was that it was the bevel that sealed the plug and the threads were to push the bevel of the plug against the bevel in the head. On a side note, another machine shop that had to take a broken off GP out, did so by drilling the prechamber out and then drilling the threads out of the GP and pushing it out.

From what I see, I am not sure that it is the carbon that was holdng my GP in. It was the steel on aluminum that welded itself together. The machinist advised me to put anti-sieze on the threads and the body of the GP but not the tip to prevent this mess occuring in the future.

The GP came out finally with one part having some thread. If you can imagine drawing a line from the middle of the threads on one side to the bevel on the oppisite side, that is what mine came out as.

In retrospect, I should have not drilled. You see, if I hit the angle right, it would be great. If not, you are screwed because you will be hitting the head. All the time we thought we were on target because the shavings coming out were largely magnetic so we thought we were all right. At a machine shop they would have the head on a bench and a drill set at the right angle and drilled.