call me stupid but why are only "old car" cams worrying about this? all cars have cams last i knew. are the "new cars" using a different steel for their cams? or is this more of a high lift high load issue?
That's a good question, most of todays engines using pushrods come from the factory with roller lifters. The flat tappet muscle motors also have some pretty beefy valve springs in them which only adds to the friction forces where the flat tappet meets the cam lobe hence the requirement for friction fighters like zinc. I don't believe that overhead cam engines have as strong a valve springs and I doubt they use dual springs. As shelby says this wasn't a problem until 2-3 yrs. ago the government got involved to reduce the zinc in oils because they believe (this is a contentious point) that the zinc harms the catylist in the catalitic converter.