[GOSFAST]

Hi Casey, they must have that radius to work correctly, without a doubt. That very slight radius helps the lifters to turn and keep a constant new oil supply on the lobe! They also (help) keep the cam positioned where it belongs, the cam lobes are normally ground with a slight taper also.

Thanks, Gary in N.Y.

P.S. Hold 2 lifters against each other, the surfaces that ride on the lobes, and they should "rock" ever so slightly. See the shot here.