I just had the timing chain on my 1988, 420SEL, V8, 4.2 liter, 116 engine (75K miles). The work was done at a Mercedes dealership. The chain and chain tensioner were replaced but no rails as I had expected. I understood that it was an imperative that the rails be replaced but the service consultant said the rails showed no wear and needn't be replaced. Have I misread the need for rail replacement? Am I facing a rail failure and subsequent chain breakage? Or, am I just a worry wort?