[reises_pieces53]

Today I tried to set the timing on my 1983 380sl. The problem I am having is the timing mark is jumping ahead 10 to 15 degrees. At ideas on what might be causing this?

 

[jaymaynard]

Assuming you have a US spec 380SL, the timing should be checked with the vacuum line unplugged at the distributor (to disable the vacuum advance) and the A/C turned off. At idle, it should be at TDC.

Are you seeing an advance of 15 degrees? (So it's firing at 15 degrees BTDC?)

 

[reises_pieces53]

AS the car is Idling and I am watching the timing mark with the timing light. The mark moves 10 to 15 degrees

 

[jaymaynard]

It's wandering that far while it's running? As in not staying in one position? Is the vacuum line at the distributor unplugged for the test? (Be sure to plug it up with something while you're testing, and plug it back in once you're done.)

Something sounds fishy...

 

[cushjbc]

If you have access to another timing light, use it to eliminate that as a cause before you tear into it. If the step above (post #4) solves the problem, have a look at the switchover valve (item 43 in the attached image).