Records show this 83 380SL had a complete top end job 40K
ago, including chain guide rails and double row chain. I'm
the paranoid type so I pulled one valve cover to verify.

Chain has been upgraded to a double. But rails are the
dark-brown old beer bottle color. No rattle audible on
startup, but when it happens, these will probably shatter.

So near and yet so far. Am I letting myself in for a
stack of grief by ordering rails and a tensioner from
the PartsShop and going after it myself? Fairly smart
and procedural DIY worker here with good toolkit and
calibrated torque wrench.

On the other hand, I'm not entirely sure of what's
entailed. And the oil consumption is up. Likely shot
valve guide seals. Rather than try that myself I'd take
it to a pro wrench, and rails seem to be a reasonable
thing to have done at the same time.

Ron H

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The rails fail due to engine being turned backwards Or from timing chain TENSIONER failure. Yes they get brittle in 4-5 years. Not really a diyer.