I believe there is a valve adjustmenton the 450SL. I hang around my clients import repair shop that specializes in Mercedes Benz. He did a valve adjustment on a 450SL one day when I was there. I don't remember what year the SL was, I think it was a 75. The car had the cams replaced and a valve job. I remember what fun they had reinstalling the exhaust manifolds. It is something that is learned from experience. Bert said SL stands for SUPER LOUSY to work on.

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1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T