I switch from a early Mopar Chrome box race ignition with the blue heat sink and the proper Accel race coil to a MSD 404B and the special Mallory race coil, Pt# 28880, in my old 1970 hemi stocker, it started better cold, it idled better cold and it ran better in high gear in the summer when the L.A. basin was smogged in
The spark plugs lasted forever also
I don't remember exactly how much better, probally close to 3 MPH in the summer
That nose heavy car(2160 lbs on the front tires, 1280 on the rear with no driver and a half tank of gas
) was a turd leaving the starting line, 4 speed on nine inch tires
They call that getting experience
I have used the MSD race boxes ever since, none of the street and strip 5 or 6 sereis boxes
As already alluded to, if you have enough spark to light the fire, adding additional spark will not give measurable results, usually
I also ended up opening the spark plug gap at the same time that I switch boxes, went from .035 to .090
I later went back to .045 with the races boxes and resitor wires and resitor spark plugs
The 7 sereies boxes need the resitor wires, the earleir 404 race boxes didn't
