If the piston travels 0.666mm per degree of crank
That is a seemingly logical jump to the wrong hypothesis I think. The piston moves at a varing rate because of the eccentric position of the rod journal. At the top and bottom of the stroke, the crank moves several degrees with very little up and down movement of the piston. At the center of the stroke the piston is at its most rapid travel.
To calculate what you are considering, you would have to remove the head and measure the movement in the range you are considering and compensate accordingly. But the piston bowl will be in practically the same place. Exact compression, turbulence / flame progression, and other factors will be of more importance than spray pattern relative to the bowl position.
Probably the most effective process is to test HP with the various shims and different advance and then decide from that. Even that will allow some variable to creep in if you can't control ambient air pressure and temperature during the entire test.
I would be more inclined to think that the different thicknesses are for machining differences between the various parts involved. Again, you would have to measure the depth of the injector and then with some run/test time to compare performance, make a decision as to what is best for your application.
As I note from the posts, some owners really like the smoke. Others want HP and nothing else. Some are quite satisfied with the noise of a straight exhaust. Pick your poision. Just start with a first gen Dodge.
1stgen4evr
James
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