It is exactly this flat tappet non roller cam lifter problem that sparked my original question.
I do have some older flat tappet engines and I have seen very serious damage to cams recently, well after they were well broke in.
I also am concerned with my diesel non roller valve train AND my injector cam also non roller. This has got to be of some importance in selecting engine oils. The failures I have seen are with Royal Purple and Mobil1 both had always performed perfectly in their past formulations.
I have been running Mobil Delvac1, BUT I understand that the zinc additive pack has been reduced or will be eliminated soon in it. KennyV.