[QUOTE=ericgr]After getting my 1984 380SL in perfect running condition in every respect (tons of power, ice smooth idle, just a pleasure to drive) I now have something that is worrying.

I suspect that the answer from the group is that I have to go in there, remove the valve covers, and look at the tensioners. QUOTE]

I hope you find something minor wrong but I would pull the valve covers and look at the guides before driving it again. Chain tentioners are about $100 US and guides are $10 each. Valve jobs are $3 to $5 grand. Check the chain guides first.