Australian W123 280E Timing

[cheezels]

Hi all, new to the forum, so g'day!
My son has a 1977 280E. He adores it, but the idle is lumpy.
I plan on doing a full tune up, but wondering if someone could advise the correct dynamic timing for 110.984 engine please?
I keep reading different values on various forums, so am a bit confused.
Also, is the Austtalian engine the same as the US engine with all the smog equipment? I can see a vapour canister and egr.
Lastly, does anyone know the horse power of the Australian model?
Many thanks in advance

[Frank Reiner]

Originally Posted by cheezels

Hi all, new to the forum, so g'day!
My son has a 1977 280E. He adores it, but the idle is lumpy.
I plan on doing a full tune up, but wondering if someone could advise the correct dynamic timing for 110.984 engine please?
I keep reading different values on various forums, so am a bit confused.
Also, is the Austtalian engine the same as the US engine with all the smog equipment? I can see a vapour canister and egr.
Lastly, does anyone know the horse power of the Australian model?
Many thanks in advance

G'day, indeed.

The .984 is a bit of a lout, but as you get into a tune up if you keep your cricket bat at hand, you may be able to keep its attention.
Unfortunately, the .984 is a 8:1 compression engine, and was delivered in the USA, AU, and Japan for emissions purposes.
First off, adjust the valves; and if you err, err on the loose side. Then confirm that cranking compression pressure values are even and ~165psi (or better).

If all's well with the valves & compression, then put the ignition components in top shape. Does the distributor have points, or a magnetic trigger? Total advance above 3500RPM, vacuum disconnected = 36-40 deg BTC.

The last step is to deal with the injection system.

[Usaguy]

Originally Posted by Frank Reiner

... Total advance above 3500RPM, vacuum disconnected = 36-40 deg BTC...

That sounds way too advanced.

It's 26 degrees @ 3,000 rpm vac. disc. according to what I found

[cheezels]

Thanks fellas

So the 984 is low compression. What pony power would that be?

So now I'm uber confused with timing. 26 degrees to 40 degrees at either 3000 or 3500??

Pretty sure it's points Frank. Part numbers suggest this, but I haven't physically checked.

[Frank Reiner]

Originally Posted by cheezels

Thanks fellas
So the 984 is low compression. What pony power would that be?
So now I'm uber confused with timing. 26 degrees to 40 degrees at either 3000 or 3500??
Pretty sure it's points Frank. Part numbers suggest this, but I haven't physically checked.

On a good day the power (new engine) would be about 170 (SAE gross).
Do you have the distributor part no.?

[cheezels]

Thanks Frank
I haven't yet got the distributor part number, just the cap part number if that helps?
0290004501
Many thanks

[cheezels]

Hi Frank
Part number for the distributor is 0237302002

[Frank Reiner]

Re: 0237302002

That distributor has a centrifugal advance range of ~25 deg., all in above 3500RPM.
With an initial firing point of ~12 deg. the total centrifugal advance (no vacuum) = 37 deg. which is within the above stated range of 36-40 deg.
At light throttle openings the vacuum will pull the total advance into the 40s, however as soon as the throttle is opened the total will fall back into the 30s.

[cheezels]

That's great Frank, many thanks. I guess I can retard a little if I hear pinking, right?
Could I trouble you for one more question.
I'm not familiar with this type of distributor. I assumed there were "points", so what checks/maintenance can be done with this one?
Also, how is dwell adjusted, and what should it be?

[Usaguy]

Originally Posted by Frank Reiner

.. the total centrifugal advance (no vacuum) = 37 deg. which is within the above stated range of 36-40 deg.
At light throttle openings the vacuum will pull the total advance into the 40s...

That's too advanced and actually for his engine it should be 32.

Check out this chart:
https://forum.w116.org/index.php?action=dlattach;topic=13940.0;attach=8958;image

Originally Posted by cheezels

...I assumed there were "points", so what checks/maintenance can be done with this one?
Also, how is dwell adjusted, and what should it be?

You have a magnetic pickup and you can't adjust the dwell. It's all done by the electronic ignition module.

[Frank Reiner]

Originally Posted by cheezels

That's great Frank, many thanks. I guess I can retard a little if I hear pinking, right?
Could I trouble you for one more question.
I'm not familiar with this type of distributor. I assumed there were "points", so what checks/maintenance can be done with this one?
Also, how is dwell adjusted, and what should it be?

Selective retarding is, indeed, the answer. The 8:1 engines are, however, rather immune to pinking.
As noted by ct, that distributor contains a magnetic pickup, and there are no dwell adjustments.

[Tomguy]

In my personal experience, advancing the timing further (and backing off if needed, rare) is the way to go on these vintage MBs. Plus you can always run a higher octane fuel. The performance (and often economy) gains are well worth it. With an 8.0:1 compression, chances are 37 degrees of timing will not be too much even on such an old engine.

[cheezels]

Thanks guys, this is awesome stuff.
Regarding the dwell not being adjustable, how is the electronic module checked for good operation?
My timing light has a dwell function, so I guess I can just go ahead and check using the light, right?

[Frank Reiner]

ch:

Dwell at lower RPM can be in a rather wide range; @1500 = 33-51deg.
@5000 = 45-55deg.

[cheezels]

Thanks Frank, much appreciated.
I have a INNOVA 5568 Pro-Timing Light that has a dwell checking function.
The instructions mention that this should be connected to the negative of the coil.
My Haynes manual mentions several precautions to be observed with transistorised ignition systems. One of which is
"Do not connect a suppression condenser to the coil negative terminal"
I'm assuming that the timing light dwell connection will be OK, right?
Sorry for all the questions. I'm a Marine Engineer so handy with the tools and big engines but car engines are not really my "wheelhouse"