Dave,

The 10mm hole you mentioned would convert to .3937". If a standard glowplug has a 1/4 X 32 thread this would only leave 0.1437" worth of material for threads. This is a pretty narrow margin as you indicated.

I just ordered my engine so I don't have it here to examine the inside of the combustion chamber. Does it look like there's enough room in the head to drill and tap for a standard 14mm spark plug (adapter)? If not I may have to devise a way to modify a glow plug to fit the 10mm hole (ie braze the threads and recut the threads). I guess another alternative would be to weld the current spark plug hole in the head closed and then drill / tap for the 1/4 X 32 glow plug.

Let me know what your opinion is. The weight of the four cycle will definitely benefit from the elimination of the coil and mag.

Hmmmm this discussion of modifications to the glow adapter makes think that a Lanova chamber conversion would be a good alternative for the diesel lovers out there....wonder if anyone has already done it.