Make the crank mark line up with o (TDC). Turn both cams so that the key is lined up with the mark on the thrust washer and it is lined up with the mark on the cam stand.
keep all of the slack out of the chain on the drivers side of the engine and slide on the chain. install the tensioner next and rotate the engine by hand and recheck timing...if it is off, just move it a tooth.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS