I once tested one of our local cars we have here that I played with for years, six cylinder engine, but still I think applicable.
Bore 92mm, stroke 76.2mm, 41.1/36.0 valves, pushrods, etc.
Anyway, going from helical gears to straight cuts, and an elec fuel pump instead of mechanical, gained (drum roll please......) 1.1/2 tenths and 1mph on a mid-15sec car.
I even reversed it all to double-check. See? It really IS a power mod.
But really I just like the whine too!