You don't need to break the chain, but you will need to pull the slide rails out to get the head off. You are going to need an impact or screw-type puller to get the pins that hold them out. You will also need a valve spring compressor, and 17 and 19 mm hex bit sockets to undo the chain tensioner.

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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