It is possible that the chain jumped and you are hearing the pistons colliding with the valves. It would also explain why the car isn't starting.

There's one tensioner on the 380, front of the right cylinder head. It has two bolts. You unbolt the old, and install the new. I use a longer bolt on one side to pull it in far enough to get the other bolt started.

But before you do anything with the tensioner, pull the right cover off, bring the engine to top dead center, and check the marks on the cam to see if it jumped.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe