One of the most important yet overlooked maintenance procedures on the Mercedes W123 is the valve adjustments. The valves need to be adjusted properly otherwise they may not open enough to draw sufficient air into the combustion chamber and/or close completely to create an effective seal giving correct compression in the chamber. These clearances are set by the space between the tappet and cam lobe when the lobe is furthest away from the tappet and there is no pressure between the lobe and tappet. If you have a tired running motor and have never adjusted your valves you may find that something as simple as adjusting the valves can make the motor feel brand new with a remarkable increase in power. Pelican recommends adjusting your valves every 12,000 miles or once a year. It doesn't take long to do, especially after you have done it more than once and for the cost of a new valve cover gasket it's a great way to insure the performance of your engine. Before you begin this procedure, please see our article on Valve Cover Gasket Replacement.

You will be working in a confined space and will need two 14mm wrenches that are bent on an angle. These are easy to make and we will show you how so you can save some money and not have to buy the special Mercedes wrenches.

IMPORTANT: Make sure the engine is stone cold before adjusting the valves; in theory it should sit over night before attempting to do this. The valves' train and cams are susceptible to thermoexpansions and the adjustments have to be done with everything cold.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users.

Read the full article:
https://www.pelicanparts.com/techarti...

Time: 13 Hours
Tab: $5 to $25
Talent:
Tools: Feeler gauges:https://www.pelicanparts.com/Mercedes..., 22mm, 14mm bent wrenched (2):https://www.pelicanparts.com/Mercedes...
Applicable Models: MercedesBenz W123 (197785)
Parts Required: Valve cover gasket:https://www.pelicanparts.com/catalog/...
Hot Tip: Take your time
Performance Gain: Proper functioning valve train
Complementary Modification: Replace valve cover gasket: https://www.pelicanparts.com/techarti...