Valve adjustment procedure on a 4.5
 

HELP!!!! I've searched the forum with no luck. How do you adjust the valve clearance on a 1975 450SL? From what I've researched, there is a threaded bushing that threads into the head, and a valve adjusting screw that threads into the bushing. From what I've read, you simply turn the adjusting screw to adjust the clearance, and there is a built-in friction in the bushing that keeps the screw from loosening. No lock nut to loosen.

I've tried to turn the adjusting screw on several valves with no luck. They are extremely tight. What am I doing wrong? :confused:

You really need the special crowfoot wrench for that job. Turning torque is fairly high, and the special wrench has a recess so that it fits the rather thin flatsa and won't slip off the adjuster. You can use a standard crowfoot, but please take a minute or two and grind the bottom flat so that there is no radius in the opening. This will reduce the tendency to round off the flats.... Turn only the upper thin flats, the lower portion is screwed down pretty tight into the head.

You can push the rocker arm off after removing the retainer spring and use a standard socket to turn the screw -- this will, obviously, take considerable time, but is better by far than tight valves.

Peter