Ign Timing

[sean sherry]

I cannot find the correct Ign. timing for an early or late 6.9 anywhere on the net. What should it be ? anyone ?

With Ant's Cars, I now believe that the early Car is to far advanced at 30% max. Mechanical , no vacuum. It pings badly.
And " 20" draw on a Vacuum gauge at idle

The later car was too far retarded. only 9 on a vacuum gauge and sounded flat.
I'm having another look this morning.

 

[CraigS]

6.3 or 6.9 ?

6.3 is 26 to 32 before TDC at 3,000 rpm depending on distributor, vacuum off. It is pretty similar for the 6.9. I set them at 0 for idle. You need to adjust from there to find the sweet spot.

 

[PvD]

Sean, Have attached Mercedes-Benz Service Technical Data Passenger Cars January 1981 Edition for models 107, 116,123 & 126 timing inforamtion. Information is for engine 100.985 normal compression and low compression (NV) standard version with two different distributors and engine AUS engine 100.985, 110, 115 and 117. The data for normal commpression 102, 110, 115, 116, 117, 123 plus J, S and USA cars are also included if anybody need them. Hope this helps.
Regards,
Peter

 

[sean sherry]

Thanks Craig.
..Timing can be a tricky business when detailed information is not available. The vacuum method gets you into the ball park. Ant's Car with the 9 vacuum reading , now 14 vacuum , he reports is much livelier and doesn't ping. The other one with 20 vacuum reading and 30% max. vacuum disconnected and pinging badly, is too far advanced, probably by at least 5%. He is going to retard it to get a vacuum reading reduced to 14/15. Then check the timing, it probably should be about 25% max, mechanical only , and around TDC at idle Hot.
They are both old style engines with high miles , so it can be a case of suck it and see !
He will let us know..

 

[CraigS]

Yes - lots of variables, such as electronic ignition, unleaded fuel, wear on the rings, injectors, timing chain, etc. so it is not at all straight forward. As I said to Ant, set it to 0 degrees and tweak it from there.

 

[PvD]

Attempt 2 at sending attachments this is first half of previously upladed bit.

 

[sean sherry]

Just as a matter of interest ... I checked my vacuum reading "Bible" and with a flick to wide open throttle the needle should drop to 2 and rebound to 25. and then settle at around 16. ....Which I knew was for a good engine ... But Ant's car was reading down to zero, with a rebound to 20, then settling to 14, and steady.
Apparently no particular problem ,, just indicating some wear and tear in the high mileage engine which performs well.

 

[Styria]

Attempt 2 at sending attachments this is first half of previously upladed bit.

Thanks for that info. Peter - it was a pity that the rain spoiled our day to some extent. I still don't know the colour of your car. There just wasn't any opportunity to tyre kick on the day. You have seen Sean's and Craig's efforts on Anthony's cars - how does the tune of your car compare with Sean's findings ?

I have never subjected Gleaming Beauty to a vacuum test - I must try this some day just to see how she stacks up. Regards Styria

 

[PvD]

Michael have attached the best photo I could find to resolve your colour dilemma. I have not checked the vacuum or timing I am just happy it is running after the work on the suspension hydraulics including new spheres, replacement of hoses, replacing front level control, cleaning reservoir and new hydraulic fluid. I have the push button working to run the fuel pumps with the iginition in the ON position before cranking the starter motor. I will fit the pressure transducer to monitor the fuel pressure next. Then I will tidy up the fuel bits near the fuel tank, replace some of the ignition components and check the timing and vacuum. Hopefully after this work the car will be reliable untill the next issue arises.
Regards,
Peter

 

[abl567]

Today I finally had a chance to take my 6.3 for a drive after Sean, with Craig's assistance, tuned it on the vacuum gauge.
The result, very light pinging on WOT uphill only A dramatic improvement!
The 450SE is also performing so much better after correction of retarded timing, rich mixture and a high idle, it is much more lively and responsive to the throttle.
Thanks guys!

 

[sean sherry]

Before you hook up your Vacuum Gauge Styria have a look on the Net and print out a Vacuum Readings Chart. There is one that is much more comprehensive than some of the others.

Did you just set the timing by a Vacuum Gauge Ant ? Where did the timing end up at Idle and Max Mechanical ? Vacuum line off ?
The idle vacuum reading is not always accurate as the idle mixture will effect it if it is not correct. I have found that checking it at 1500RPM Hot is more accurate, followed by a Timing Light check.