mercedes have been using valve rotators since the 1950's. Even the 1956 220a i have has them. They are designed to promote both even seating and cooling and to prevent the seats from gathering bits of carbon that build up on the stems creating a worse problem,valve sticking. I have just finished the worst one I have ever seen today. The valves were jammed in the guides and pulled them from the head. The remains of the guides were going up and down with the valves and the build up of burnt oil deposits had blocked the ports. It still ran but the smoke would have given Al Gore a heart attack.