I just went through my box of 'late model" stuff in the garage. Found one (Duraspark upper rotor shaft) that has a 13L slot on one side and an 18L in the other. The 13L slot measures .430 - .4375 is 7/16". Get out your file! That would give you a 26° plus your initial.I can hardly believe you can get away with 40° total - if I tried that on Arizona gas everything I own would rattle like a box of marbles.