I'm having trouble understandng the necessity of the valve rotators on my "67 230.. It appears (from a Haynes book) that MB did not continue them on the 280 but that could be an error. The majority of my research indicates that very few modern ICE's have them any more yet small airplane engines (Lycoming, Continental) appear to continue with them. Opinions needed on leaving them off my rebuilt head. I could upgrade the valves and springs to more modern tecnology more easily if valve rotators weren't required..