Just noticed you said you turned the mixture screw clockwise, that will richen the mixture, CCW leans it out. 1/2 turn is a lot. I turned mine about 1/4 turn with a DMM hooked to the 02 sensor, got a .42 volt reading and blew thru emissions in MD. They did not do the NOx test, only HC and CO.

I’ve read the whole article and sort of understand it. But with the vacuum line plugged the timing advances.

What would be great would be a video
Upload to YouTube or something of the whole process.

My 74 450SL says it’s supposed to be set to 5 degrees atdc with vacuum connected. I’ve been dealing with an overheating issue believed to be caused by incorrect ignition timing. The AI internet searches says that advanced OR retarded timing can cause overheating… so I’m torn and stuck on what to do. Most of the videos I’ve found dealing with setting ignition timing only sets the initial timing. If I could see it be done I could better understand what to do when the vacuum line is pulled from the vacuum advance on my 74’ 450SL to set the timing….
Thank you.

The chart on the service manual says 10-14 degrees btdc 1500rpms and 18-22 degrees at 3000rpms.

I am no mechanic but I can sort of understand mechanics and how to take something apart and tinker.

How to correctly set timing on 107??

1) Follow the instructions given by page 62 in post #5.
2) After setting the centrifugal advance timing connect only the advance portion of the vacuum diaphragm unit. Leave the retard section w/o vacuum.

I believe the 1974 450SL has the vacuum retard connection port