Pete_Muller
Moderator
I could be off-base here, but I believe most automotive cams have a very, very slight taper in the cam lobes, and the lifters are ground to a 60" radius... or maybe it was a 60" circle. Bottom line is that I believe the goal is to match the very tiny taper in the lobe close to the radius on the lifter, and this causes the lifter to rotate a tiny bit with each valve lift. This prevents the lifter from getting worn from sitting in the same orientation all the time.
PM
PM