There are, but the Rover V8 is hard on its tappets and cam lobes for some reason - I'm not saying it's a great design but when it was designed in the 1950s there was plenty of zinc in the oil. I had plenty of experience of 200,000 mile+ Rover V8s in the 80s with no cam issues - ring wear used to be the issue along with oil pressure problems caused by sludge - this cam problem seems to have appeared with vengeance since the early 90s when catalysts became mandatory and zinc was simultaneously removed or massively reduced in oil.