You remove the rocker arm and then remove the ball stud with a large (27mm?) deep-well socket. The "hockey puck" sits on top of the valve stem/spring and comes in various thicknesses to pre-tension the ball stud.

The noise could be coming from the rocker or the ball stud.

You should check the pretensioning of the new rocker/ball stud with the special tool, but if it still rattles, go with a thicker puck. The come in seven thicknesses.

It would be a good idea to replace the oil tube's plastic pieces while you are in there.

__________________
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