Well then by all means just replace the tensioner. It is located just above the oil filter housing, mounted into the front of the right head. Two bolts.

But, just like mercedesdoc said, your 380SL is most likely in need of new upper chain guides and possibly a new chain. I have repaired two engines that have cratered due to any of the above mentioned parts failing, not a pretty (or inexpensive) sight.

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Chas

Had a 380SL, 450SL, 380SEL, 420SEL, 500SEL

Got a Euro 500SEC right now.