I just adjusted my valves on my 1973 450 SL. The car has 183000 miles on her. I noticed the timing chain seems a little loose at certain spots on the rotation during the valve setting. There are spots where I can pull the chain away from the upper rails and touch the head casting. I have read some threads that say the Chain Tensioner is supplied oil to create pressure on the chain. Is this correct?? If that is true, then can someone tell me how to check chain stretch on the car using the crankshaft pulley? The guides I can see with the valve covers off, all seem ok. I am wondering if the chain tensioner is not functioning correctly. Previous original owner says she had "valve work " done some years ago around 145000 miles, but can't recall just what was done.

Thanks,
Mark

To check chain stretch, rotate engine until the right camshaft alignment mark and the mark on the cam tower are matched up -- nominally TDC on the crank. Look down and see how many degrees the crank is after top dead center -- this is the chain stretch (wear) in degrees. Less than 8 degrees is fine, more, replace the chain.

If the chain is sloppy, the tensioner is leaking down and should be replaced or repaired -- the internal o-rings are shot. Not too hard to do, it is under the alternator below the head on the front cover. I'd fix it, a slapping chain can break the upper guide, and that usually gets in the chain and breaks that, bends the valves on both heads and costs $$$$$.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!