I tried running the Fire Core distributor. I set the base timing at 18 and set the mechanical advance at 16 which gave me 34 total. Using 2 blue springs the mechanical advance started at 1100 rpm and the mechanical advance was all in by 2100 rpm. I test drove the car with part throttle runs taking it up to 4000 rpm and I don't hear any detonation. Can detonation be so slight that it would be hard to hear it? Is 2100 to low for a street engine. I double checked my MP unit and it was all in by 2500rpm. Should I change the springs to heavier ones?