ORIGINAL: DarZeelon
This head seems like a lousy piece of engineering...
The glow plug is at an angle to the area of the combustion chamber it exists through...
This could potentially put threads in the 'line of fire', to become 'hot spots'.
This is not the engineering these engineers learned in the university...
I am very surprised, in the negative sense.
It seems to me the hole is drilled in steps and the threads were only supposed to be in the upper step, not in the lower area. Sounds like the tap was not run all the way through and that resulted in a taper with shallow threads at the bottom. As for its location, it is exactly where it should be, between the valves and on the thicker end of the wedge.