ORIGINAL: Sandore
... About my "don't laugh" comment regarding my homemade glow plug head, I don't know about the general sentiment, but I can imagine that as a non-engine expert, and a non-machinist, my attempt is not likely to work all that well. I had fun making it though, and if it ever runs with my head I will be tickled. I think one of those Galbreath heads may be in my future. I've done the fuel tubing slices thing, but I will keep trying.
The big difference between the standard plug and the Galbreath/Nelson or the Turbo is that the standard plug seals at the top of the threads and has a larger plug cavity (where the coil is) whereas the Nelsons and turbos seal at the bottom and have smaller cavaties. The results is that the standard plug increases combustion chamber size which, in turn, decreases power.
If you have room in your head to fit an idle bar, it is probably sitting too high. If you want to try your head (after the engine is running) have it fit so the bottom of the
standard short plug is level with the combustion chamber...neither recessed nor sticking out.
George