7-17-07 re-loaded Matt Merrill's information
6-30-07 added information by "merrill" (Matt Merrill)
11-19-06 intake venturi linkage information added
11-17-06 accelerator pedal linkage info added
11-16-06 information corrected, thanks Matt!
4-4-06 updated (parts numbers added)
There has been a lot of information posted on the subject of linkage adjustment. Thought it might be nice to have it all in one document with photos and diagrams. I have added factory information and what I know on the subject. Feel free to add, or correct as needed.
Sorry if some of these plates have become fuzzy after compression.
The intake venturi is one of the most important aspects of the engine linkage adjustment, engine tuning and automatic transmission shifting. When not adjusted properly problems with improper idle speed, hard automatic transmission shifting, up or down and erratic engine behaviour may result. Proper linkage adjustment will be nearly impossible if the venturi is not correctly set.
The intake venturi stop screw.......
The most common and first item to check is the small slotted stop screw with lock nut on the intake venturi. This is factory set and is frequently mistakenly used as an idle adjustment screw. This stop screw must be set so that the intake linkage arm and venturi valve in the intake closes all the way! When not set correctly too much idle air will be admitted to the engine causing lean idle mixture and/or too high engine idle rpm. An uninformed person may compensate for the situation by tampering with injection and linkage adjustments thus getting the engine even further from being in correct tune. Download Attachment: venturi illus.JPG
W113s with automatic transmissions also have a electrical switch attached to the venturi. This switch lowers and raises modulator pressure by activating the three position solenoid on the transmission. Harsh downshifts (especially the last downshift before a stop) may result when not adjusted correctly. Correcting an improper set venturi can make an amazing difference in shifting, engine idle and engine performance. Download Attachment: venturi illus2.JPG
Disconnect the linkage rod going from the cross over rod to the venturi. If you have a USA version with the vacuum dash pot, you will need to move it out of the way so it does not interfere with the adjustment. The small slotted venturi set screw must be backed off enough to allow the venturi valve to close all the way and then adjusted in just enough to keep the venturi valve from binding in the intake.
USA 280SLs had an "Vacuum throttle control" on the intake venturi linkage. A special linkage with a "slip joint" was also used between the venturi and the cross-over rod on the engine. Adjust the slip joint linkage so it is fully compressed with the engine running and warm at idle in neutral. Adjust the vacuum control/linkage to
zero clearance. Now with the transmission in gear, the throttle lever will open 1.0 mm to 1.5 mm.
If you have a factory shop manual with the USA versions look on page 07-14/7. It gives the procedure to adjust the unit.
Adjustments of the other linkage and tune-up items can follow afterwards if the idle is too high or too low or the mixture is incorrect.Download Attachment: linkage 1.JPG
77.8 KBDownload Attachment: linkage 11.JPG
55.19 KBDownload Attachment: 12.3.JPG
79.63 KBDownload Attachment: linkage 13.JPG
Naj points out that linkage parts should be checked for wear and has supplied parts numbers. Thanks Naj.
127 072 0185 spherical brass bushing (2 required)
000 991 8922 rod end ball socket RHT (as required)
000 991 9022 rod end ball socket LHT (as required)
During regular maintenance engine linkages should be lubricated with a light oil. Often times the block pivot is missed and may begin to bind or seize after periods of inactivity or storage. Try using some penetrant first then oil after it becomes free. This photo is a sedan pivot. The location is the same (under the intake manifold) and the unit is very similar. Also not the factory coolant drain plug location in the picture. Download Attachment: block linkage lever.JPG
Here is some information on the firewall accelerator pedal linkage and adjustment. The linkage between the block pivot and the intake manifold lever should be checked first before tampering with the firewall adjustment. Download Attachment: pedal linkage .2.JPG
When the accelerator pedal is at the floor the venturi valve should be wide open. If not you are loosing a lot of power. This is fairly common problem. With automatics the pedal must also contact the "kick down switch". Adjust at the firewall after checking the other linkages.
Information and diagram contributed by "merrill" Matt Merrill;
"I have put the part numbers for another linkage bushing, ball stud , washer and nut.
all are available at the price in the photo. the bushings are only in germany"..........
Matt Merrill's information;Download Attachment: Merrill.jpg