My 450SL engine has 100K since i rebuilt it (car is over 200k miles). I had replaced the chain, sprockets, rails and tensioner.

Recently I started hearing a slight timing chain slap only on hot startup. took the valve covers off to check chain and rails. i rotated the engine 4 times in clockwise direction only (didn't bother removing the spark plugs) and each time I measured 12 degrees ATDC on the crank damper when the right cam marks lined up. The weird thing is that the left cam lined up almost perfectly with the crank damper at TDC (actually looks like 2 degrees BTDC which kind of baffles me). The car runs well but need your advise.


Why is one cam timed OK and the other off by so much (not by a whole tooth though)? Does the evidence suggest stretched chain or bad tensioner? Why would a stretched chain only effect one cam's timing and not the other?

The rails look fine, no cracks etc but they are 18 years old with 100K on them. I'd hate to change everything (chain, 3 side tensioners and tensioner) only to find out that something else is wrong.

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1972 450SL
1982 300D Turbo