[A26B]

I concur completely. To reduce this down would require establishing all the variables, which is a sizable task in itself. Then analyze changes to each variable independently while all other variables remain constant.

Example: Given a specific engine, lets say its completely stock, changing only plug gap on the same spark plugs can yield data specific to that singular change. Introduce a change in intake cams only. May yield different power results with the same spark plug at different gaps.

For a highly modified engine, I think it would require testing of different combinations of the variables to determine the best gap. For instance a combo of specific coils, wires & plugs, (all other variables remain constant) then vary the gap to see the result. I would expect the best plug gap to be different from the basic testing which yielded 0.042 as the best gap.

My point is, There is no best gap for all engines inclusive, but rather a general "best gap" for the mean distribution. Even stock engines vary in power output and may respond differently to plug gap, depending on coil output, Plug wire resistance, etc. For the vast majority of us without the means to determine results empirically, "seat of the pants" will have to do.