[Jim Brierley]

I've never had that problem, but cam lobes are ground on a taper to induce tappet rotation. The timing gears and the dist/oil pump gear produce thrust towards the rear. That's the theory anyway but I've found that dumb things, like iron and other metals, don't always know about theory. I also use a bolt in the plunger to control movement on my Bonneville engine but noise on a race car is too loud for me to notice any small noise.