Remove the two rocker arms of the first cylinder by turning the crankshaft to a position in which the noses of the corresponding cams are directed upward.
Replace the tappets on the valves of the first cylinder with special measuring tappets and install the valve levers without springs. Using the adjusting bolts in the valve lever supports, select the gap between the working surfaces of the cam and the valve lever.
Install and secure the device 110 589 102 100 (see fig. 96).
Fig. 96. Device for checking valve timing.
Inlet valve: with the valve closed, place a dial indicator in the fixture and secure the indicator in the fixture in this position. Turn the indicator scale to "0" against the large arrow. Slowly turn the crankshaft until the indicator shows 2...1 mm and read the readings on the damper under the indicator pin. They should match the data in the table "Opening the inlet valve after TDC".
Exhaust valve: install and secure the indicator on the exhaust valve as described above. Slowly turn the crankshaft until the exhaust valve is fully open and then, when the valve closes, note the readings "1 mm" of the small arrow and "0" of the large one. This corresponds to 2 mm of valve travel before closing.
(Article borrowed from the web portal: «MERCEDESMAN»)