I just started to hear a valve clicking noise in my chev 327 using synthetic castrol.... spoke to a few guys and seems the cam is worn and I need to do a cam shaft and relevant parts replacement... one of my friends suggested that the new oils.. synthetics were no good for the old engins because there were insufficient additives that the older engine parts need and suggested I switch to shell RIMULA whch is a oil for deisel engines but he said it would be better than the new synthetics for my old engine.. kinda sounds far out.. but if im gonna spend the money on a cam job want to be sure im gonna do the right thing or i may have to do a major overhaul