[Gravelroad]

In 1972 I worked at a place in Spokane Wa called Unit Engineering, an engine rebuild machine shop. I spent quite a bit of time on the cam grinder. Most all of the cams we ground had a taper to the lobe and the lifters were slightly parabolic on the bottom. If you held two new lifters bottom to bottom, they only contacted each other in the center. This taper of the cam lobe and "rounded" bottom of the tappet is what cause the lifter (and pushrods in ohv engines) to rotate when running. This created more of a bearing action than a wiping action We never hardened our regrinds but did tape the bearing journals with masking tape for protection and then immerse the freshly ground cam in a heated parkerizing solution for a time. This made the cam lobe turn black and take on an acid induced textured surface which would help hold oil and aid in turning the lifter. Never ground an A or T cam but assume they would be engineered the same.