Mercedes-Benz Forum banner

1 - 4 of 4 Posts

·
Registered
1973 450SL 1984 300TD 1997 E320
Joined
·
42 Posts
Discussion Starter #1
Recently needed to set ignition timing on my 73 450SL, USA model.
Tag indicates 5 Deg. ATDC at idle . Additionally, literature indicates 10-14 deg. at 1500 RPM and 18-22 deg. at 3000 RPM all with with vacuum.
Assuming the vacuum and distributor functioning correctly, which one of the above three setting is most important? Isn't it if one setting is correct the other two settings must agree too? After all one can physically, set the distributor at only one position. Or these additional degrees given only to check if distributor is functioning properly at higher RPM?

I did mine with only idle at 5 deg. ATDC and did not mark the pulley for other two RPMs.
 

·
Outstanding Contributor
450slc5.0cab 280sl5sp 280se4.5 500seAMG +250seStkW108 350sl4spdX3 500secEuro
Joined
·
22,158 Posts
I usually set them at spec 5 atdc with vacuum and make sure the vacuum retard works. Basically you should get 5 BTDC at idle when you remove the vacuum line from the pod on the distributor. The idle usually goes up a little with the advance.

The mechanical centripetal advance can get stuck and not advance the timing. So you should make sure that the timing advances well with higher rpms. If it doesn’t, the car won’t accelerate well and will be weak.

So I find myself not worrying about it if the cars drive well and are peppy.

So I check the idle timing first, and the check the higher rpms. They should all be pretty close to spec.


Sent from my iPhone using Tapatalk
 

·
Registered
1973 450SL 1984 300TD 1997 E320
Joined
·
42 Posts
Discussion Starter #3
Thanks. I did same. If necessary, I will check the higher RPM timings after a road test.
 

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
10,083 Posts
5deg ATDC with vac is what the manual says based on emission control at idle. But I would set it at TDC with vacuum at idle (700-750rpm with engine warmed up, running smoothly and A/C turned OFF). Then check the advance (With vacuum disconnected). It should get to about 5deg more than the book values at 1500 and 3000rpm. 27 BTDC at 3000rpm and the car will run great! All settings are important. The 1500/3000rpm numbers confirm that your centrifugal advance is working.
 
1 - 4 of 4 Posts
Top