Valve Clearance: Adjustments

NOTE: Check valve clearance or adjust with the engine cold or at operating temperature.






63 Cap nut
63a Counter-nut

When adjusting valve clearance and in case of repairs, check whether cap nuts (63) of the valves are secured through counter-nuts (63a).

Since engine damages may occur with the cap nuts loose, make sure to observe the following points when performing these procedures:

Check cap and counter-nuts, even on valves on which the valve clearance is not changed.






A Worn out counter-nut "H" below 5 mm
B New counter-nut "H" 6 mm

a) for tight seat
b) for counter-nut wear dimension "H" below 5 mm or for counter surfaces worn out.

In both cases, replace cap nuts and counter-nuts and counter-lock thereafter (tightening torque 20 - 30 Nm).






arrow = worn out counter surface

With nuts worn out, also check thread on valve shaft.






Check camshaft from malleable cast iron (code No. 00 or 02) for wear. If there is heavy formation of flat areas (arrow) on cam loosening of the countered nuts may be the result. If flat areas have been formed, replace camshaft, rocker arm, valve springs as well as cap and counter-nuts.

Additionally check valves, replace, if required.

NOTE: Minor formation of flat areas may occur with chilled casting camshafts (code Nos. 05, 06, 08, 10, 11, 13, 14, 15, 18 and 19) which, however, does not extend further and is harmless, therefore.






A Rocker arm, induction hardened and hard chrome plated
B Rocker arm with hard backing

Upon introduction of chilled casting camshafts and hard-backed rocker arms (B, arrow), the cap nuts were strengthened (larger contact area, arrow) and finished in hard chrome plating (B).






A Cap nut without chrome plating
B Cap nut chrome plated

They may be mounted on all rocker arm versions. In contrast thereto the non-chrome plated cap nut must not be used on rocker arms with hard-backed finish.

Salt bath nitrided counternuts are installed to improve functional reliability (phosphatized up to now). Only modified counternuts are now available as spare parts.






Production breakpoint: October 1983






Adjustment
1 Remove cylinder head cover.
On vehicles with automatic transmissions and vacuum controlled modulating pressure, additionally disconnect vacuum lines at switch-over valve.

CAUTION: Be sure not to cross vacuum lines. The pipe unions and vacuum lines are color coded.






On engines with longitudinal control spindles detach all control rods. Withdraw retainer (arrow) and force longitudinal control spindle in aft direction. Unscrew bracket (1) and unclip idle control cable (2) with plastic sleeve (3).

2 Set start/stop cable to "stop", turning ignition key to "0".






3 Check valve clearance between contact surface of rocker arm and base cam circle of camshaft (arrow). The cam peak must be perpendicular to rocker arm.

Valve clearance is correct when feeler gauge fit






Engines 615, 616






Engine 617

Note arrangement of intake and exhaust valves.

The engine can be cranked as follows:






a) Applying tool combination to forward end of crankshaft

CAUTION: Engine must not be cranked on fastening bolt of cam shaft sprocket. Do not turn crankshaft backward.






b) Using starter and remote starter switch Connect remote starter switch to terminals 30 and 50 on starter. Battery positive can be used in place of terminal 30.






4 Position holding wrench on valve spring cap.






5 Release cap nut, securing lock-nut on valve with valve adjusting wrench.
6 Adjust valve clearance by turning cap nut.
7 Having completed adjustment, secure cap nut with lock-nut
8 Check valve clearance again.
9 Fit cylinder head cover.