On my fist mercedes (W114 280) the fifth exhaust lobe was worn. With some sandpaper I reshaped it to a slightly smaller but smooth lobe and it ran great again. This process had to be repeated every 50K km. After 500K km the lobe was so small that performance was somewhat affected, the car would not run over 200Km/h any more.

I bought a W126 280S, and after some time the fifth exhaust lobe was worn (seems to be a m110 problem). This time a bought a used cam ($40) , cleaned all oil ducts and just put it in.

When I sold the car after 450K km the cam was still OK. Later I heard that the next two owners put another 200K km on it without problems.

Both these cars were frequently driven on the autobahn in Germany, as fast as they would go.

Rob