Timing setting help please - 1969 w115/220 gas 4 cylinder

[Topher39]

Could use some basic guidance on setting the timing on my 220 - I have a timing light and dwell/rpm meter, I need some clarity on setting the timing as it relates to settings/rpm and vacuume hose on or off. The car is running and at the moment I have the timing set to facilitate the smoothest idle. Idle is a bit high at the moment, again to get a smooth idle and decent warm up. The car runs well, it's a standard shift. I do get some dieseling when I shut down, I am thinking the timing may be a bit off, running a bit hot perhaps?

When I take off the vacuum hose while at idle, I do see a difference in rpm and idle - is this normal?

Some numbers and "sage" advice would be appreciated.

Chris

[Mike D]

Timing at idle (apx. 750 RPMs) 14 degrees BTDC with vacuum disconnected. Vacuum connected the timing should drop to apx. 6 degrees BTDC depending on distributor wear. At 3000 RPM, full advance should be apx. 30 degrees.

The high idle is probably causing the "dieseling" along with a likely "lean" condition common to the Stromberg carb set-up.

[Topher39]

Sounds like the first step to getting Das Benz starting and purring IS the timing, otherwise I chase my tail trying to settle balance on the rest of the variables?

Mike, at 3000 rpm do I set the timing with the vacuum hose on or off (off I believe)?

If I have trouble getting the idel that low to start with, is it an issue of the idle mixture as well as correct timing?

Will to fast a idle actually make starting up cold harder?

Thanks for your help Mike.

Chris

[meltedpanda]

Hmm, according to my MB manual a 69 220/8 should have.023 plug gap, point gap .016-.020, dwell at 48-52 850 RPM in nuetral.

Make sure cap, rotor and points are new, they are cheap.

One thing that worked for me - pull of vacuum , plug it with a golf tee, rev to 4500RPM and set timing at 43 degrees , then connect and see what the values are at 750-800RPM

that said , most of the time I just set it by feel and listening, find the sweet spot, you will know it when its found

have you adjusted valves?

[Topher39]

Timing Update - OK, this is what I have now, at this setting it does idle right about 800 rpm. Valves have not been adjusted, car sat for 4 years, since "rebirth" I have driven it around town for about 1.5 hours combined two trips) So what do you see from my numbers? Next set of advice?

Current Dwell 55 (recommended 42-52)

Timing Without Vacuum line connected:
4500 rpm - about 40 BTDC
3000 rpm - 30 BTDC
800 rpm - 20 BTDC - (recommended 13-19)

WITH vacuum connected:
4500 - 47-50
3000 - 40
800 - 30 (is this correct??)

Unknown miles on the car, figure 95,000+ (Odometer stopped at 94,000 IF original)

[Mike D]

Okay, so what you have is a vacuum advance on your distributor instead of the usual vacuum retard seen on most US cars. No big deal. With the Vacuum disconnected and plugged, idle at apx. 750-850 RPM.s, adjust your timing to 5 degrees BTDC. This will bring your timing down into the accepted range.

Usually vacuum advance is run from a "ported" source (vacuum is only present when acceleration is occurring) but for whatever reason yours is connected to manifold vacuum.

[Topher39]

Hey Mike, sure appreciate your input.

My vacuum hose is connected to the first brass nipple (facing the front of the car) out of 3 that are sticking up and out of the top of the carb's mounting face . . . is that the correct port for the vacuum? the other two brass nipples have a rubber stopper on them. Perhaps I have the vacuum line on the wrong nipple?? I have the single stromberg.

Chris

[Topher39]

Mike - another user pointed out that I have a replacement Distributor, see below feedback from Arthur (thank you Arthur):

Quote:
Originally Posted by Topher39
I believe it reads 231 170 137
What can you tell me?

Quote:
Originally Posted by Arthur Dalton
Do you have the dist # ?

A Dalton
BenzTechs




That is a replacement dist.

Orig was 0231-115-065

T his should be a vac retard dist.

4500rpm-43\3000-31-37
Idle-2.

To make sure this new dist is vac retard, start the car and at idle, check timing w/strobe...then disconnect the vac line to dist and see if the timing goes higher w/o vac, and rpm should also increase.

Replace vac hose and it should retard again.
Do this test w/o stopping engine

[Mike D]

There ya go!

I said 5 degrees BTDC and Arthur states it as 2 degrees. Close enough using either setting.

It sounds as though the dizzy situation is also analyzed. You have the wrong distributor. No biggie, just cap the vacuum line at the intake and run the car using the built in mechanical advance.

I run my M115 at 10 degrees at idle, no vacuum mechanism in use but I am also not dealing with the "Stormbird" carb.

[Topher39]

I tried the other two nipples on the carb and I found that each has just a little vacuum at a very quick/high throttle flip, but not much and low vacuum pressure.

As suggested, I tried to set the timing using just the mechanical advance of this non-original distributor, this is what I found:

1. I could not get the car to idle well at all with the timing set 10 BTDC or less, comfortable smooth idle seemed to be more like 20-22 BTDC!

2. With the idle timing at 10, I checked the idle at 3000 and timing was still in the 20s, at 4500 the timing was showing almost 30.

3. I put the "funky" constant vacuum hose on the distributor again, set the idle at the most smooth timing (20-22) and I got the following results at higher rpm: 3000/30, 4500/43

Why can't I get the timing for the idle down below 20 without degrading idle quality?? - Is this pointing to a valve problem/adjustment?

Other Issues: I do find that when the car is cold, I have to do a lot of cranking to get it to start, once started then warmed up, it will hold the idle well and runs well. Again, is this hard starting an issue of valves?
(the carb was rebuilt from the ground up, not sure that the cold start mechanism is really working)

Distributor - Mechanical advance on this distributor is not really cutting it on it's own is it, not getting the correct advance right? The car does drive pretty darn well and seems to have good power for it's age with the funky vacuum and all - as long as my timing at speed is acceptable. Where do I go from here? Should I be looking for another distributor?

Thanks for your help.

[Benz Dr.]

I've been rebuilding distributors for about 15 years and I've found that you have to match the distributor to the vacuum signal. Without a vacuum signal most units will give you 10 - 20 degrees of advance depending on which distributor you have. 20 degrees won't be enough for a 4 cylinder engine which usually needs about 40 to produce good power. You can advance the timing to compensate for that but you will have problems with keeping the idle speed down.

Vacuum advance builds with engine RPM while vacuum retard disappears as engine RPM increases. Some systems have vacuum switch over valves which may have been employed on your car but may now be missing.

If you can find a 190SL distributor which gives 30 degrees mechanical this could work for you. If you find that the fly weights aren't working properly there's a good chance someone used a screw that was too long while mounting the condensor and it bent the arms which hold the return springs. This can be fixed sometimes.

Excessive wear at the bearings, combined with advance plate wear and top shaft wear, will make your points close up at higher RPM's with resulting dwell angle loss as well as timming loss. 55 degrees of dwell means your point gap is kind of close and you might want to open them slightly.

Your distributor has to function properly or the engine will never run the way it should. Having your distributor rebuilt is a common and very much over looked detail during engine tuning and restoration of older cars with these ignition systems.

[meltedpanda]

Benz Dr is correct, also have to add shaft wobble with worn distributors as an issue as well. Not sure if it is available but have you looked into retrofitting an electronic ignition , did this on my SL to compensate for shaft wear. I used a pertronix unit

[Topher39]

The good news is that as I check the Dwell with my meter it stays put through low and high rpm - that is a good sign yes?

I am going to look into my carb to see if that is the reason I can't get the car to idle well at the correct low rpm timing setting. As I said, anything below 20 BTDC at 800-900 rpm and the idle crashes.

[Topher39]

A small update for today, I pulled the cold start device which I had totally cleaned when I rebuilt the carb. At the time of rebuild, the small piston that controls the cold start fuel squirt/enrichment was binding and it would not travel up and down correctly. At that time I polished the piston and got it working BUT, I did notice that the tollerance is very tight as it would bind when I tightened down the entire cold start device. Today, as expected, I found the cold start piston locked in the up or NON enrichment position - so all this hard starting and excessive coaxing to start is at least in a major part caused by the cold start complete failure. That was the issue I mentioned I need to look into.

As I said, the car runs really well once started - despite the whole timing head scratcher.

I think you may be onto something whith the stretched timing chain - perhaps the timing is not that far off but the indicators are.

Chris

[Topher39]

Question - will the 190SL style distributor fit my 220/w115 OK, and do you think that that extra advance will make a big difference in power?