Zinc

I`ve read the same thing that Mopar Dave said. Too much ZDDP can be as bad as not enough. An overdose can cause gauling on cams. Flat tappet cams are cast iron which is very porous. Seen under a microscope these cams look like the surface of the moon. The small particles of zinc embed themselves in the nooks and crannies of the iron and help to smooth out the lobes. Modern roller cams are cut from steel billets and to start with are much harder and smoother surfaces and of course use rollers on the lifters instead of direct contact as found with flat tappet cams. One must remember that zinc is a metal and if used correctly, can help with the smooth operation of flat tappet cams/lifters. On the flip side you wouldn`t pour a jar of iron filings in your engine, so go easy with the ZDDP and find an oil that`s formulated correctly and skip the guesswork.