The cam followers (tappets) on the 3 1/2 litre engines have a convex surface at the side engaging the cam lobe. This characteristic “mushroom” shape has about 0.001" droop at the tappet radius, i.e. when a tappet is placed with mushroom top down on a flat surface the tappet stem can rock back and forth because of the convex tappet surface.
I have the impression cams are designed to follow the convex cross section of the tappet, i.e. the cam lift changes along the cam surface in contact with the tappet. This sometimes is called a linear cut and would have about a 0.001" difference from one side of each cam lobe to the other side so as to match the mushroom convexity?
A couple questions arise.
A cam lobe offset from the tappet center line would induce tappet rotation whether flat or convex?
What is the function of this convex tappet surface and the corresponding cam grind? Both surfaces require extra machining and cost, so it seems there must be a reason. Would the angle of the convex connection create sideways force on the tappet surface to offset the torque-induced bend from the vertical tappet motion and thereby reduce or eliminate tappet guide wear?
A spare used camshaft on the shelf shows uneven wear on the lobes, each lobe with one end shiny and the other end dark. Methinks this camshaft was ground straight and not fit to the tappet convex shape at one time long ago.