Interesting discussion, here is my 2 cents: With the single pattern cam both the duration and the lift are exactly the same for both the intake and exhaust. Dual pattens are all freaky and complicated because the intake and exhaust can share the same duration but have different lifts, or they can have the same lifts but with different durations, or best of all, both intake and exhaust can have both different lift and duration. There is an almost infinite # of combinations with dual pattern cams so how people come up with and choose their own custom grinds is beyond me and would be interesting to to hear about.
Dan
