W113 Pagoda SL Group > W11x chassis cars

280 SEL two way valve / distributor

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dirkbalter:
Hello,
A little while back I bought a 1970 280 sel, which I am using as a daily driver mainly back and forth to the office.  (It should be similar to a late 280sl).  The car runs nice but had the idle speed set to high. In an attempt to address the problem, I first went through the linkage adjustment procedure to insure everything is good there. After that, I looked into the ignition timing. (The car has transistorized ignition, blue coil with a 066 distributor).
I recognized that the two-way valve had one vacuum line going to the distributor but no line coming from the manifold. The manifold nipple had a plug. In other words, no vacuum was going to the distributor.

I red through the threads in the forum and found:
https://www.sl113.org/forums/index.php?topic=10806.0

Following the advice, I first checked that I have 12V at the valve at idle.
 I don’t.  (the valve itself if I apply 12V, switches fine. Measuring 16-17inHG)
I than bypassed the valve and ran vacuum direct from the manifold to the distributor. (Timing at 8 ATDC with vacuum). The car starts and runs well but I have excessive “pinging” under load at low rpm’s.

I reverted back to my original no vacuum setting with the timing set at approx. 0-2 deg BTDC (750 rpm) and close to 20 deg BTDC @ 3000 rpm.  The car runs relatively good in that set up. However, I am probably losing power and efficiency at higher speed.?
To the experts: how exactly does the valve / vacuum relative to the distributor work? 

What would be the best fix? (I am not too excited about the whole emission system with all its problems as it ages). 
My distributor, also not bad, has a little play between the shaft and the bushing. I was looking into a 123 system.  Am I correct in assuming the 123 would take vacuum direct from the manifold to operate?

Any opinions and help would be greatly appreciated.
Thank you
Dirk

ja17:
 You should have at least 30 degrees BTDC at 3,000 rpms or your giving up a lot of power and fuel economy. Another option would be find the "vacuum at idle" port on the intake and hook it directly to the vacuum retard on the distributor.  This way when the throttle is opened, the vacuum retard is released and the timing is advanced. You should then be able to set the timing close to spec  at idle and at 3,000 rpms. Power and fuel economy will return.  As a consequence, you will have by-passed the cold idle emission timing feature and the hot running timing feature. No big loss unless you are suffering from some hot running problems. The 123 distributor is also a good option, but you may still be faced with restoring the emission timing features or by-passing them.

Benz Dr.:
That will work as long as you have the right vacuum port. If you have a constant vacuum throttle body it won't work. One option would be to go back to an earlier version throttle body and then you can use a variety of different distributor options.

dirkbalter:
Thank you, Joe and Dan, for responding and your advice. I made the mistake to assume the vacuum is highest at idle and as rpm’s increase the vacuum decreases. (I thought I red this somewhere but should have checked that).
I attached a vacuum gauge and as you pointed out, I have constant vacuum going to the two-way valve as well as to the dampener. (Actually, the vacuum increases from around 15in at idle to about 20in at higher rev’s). So now it all makes more sense to me.
Based on what you said, I have the following options:

1)   Fix the problem with the two-way valve that is not actuating and shutting down the vacuum at a certain rpm. This is probably not as easy as it sounds. I am trying to read up on it and from what I understand it involves a couple of relays. Has anybody had a similar problem and has attempted that and have some advice? 
2)   Joe said to find a “vacuum at idle” port in the manifold. I am not sure where to find that or if that can be added? (Probably the easiest)
3)   As per Dan: Replace the throttle body with an older one that has the “vacuum at idle” port. Does anybody have an “older” throttle body for sale?
4)   Something else?

Thank you for your help
Dirk

Pawel66:
I am sorry to interfere - I am following this thread just for learning... to perhaps better understand (also for myself) what Joe wrote (about directly hooking vacuum from throttle to distributor, with valves, emissions - I have no idea):

Have you studied this: https://www.sl113.org/wiki/Electrical/Distributor

You will find there an explanation related to vacuum in the inlet manifold and throttle - higher or lower, it depends on where you look and where you take it from. In the text you will find reference to throttle body and if you follow this one, you will see the two types of throttle bodies,  as well as ports locations.

If you have late, retard distributor, you then have to have the retard vacuum throttle body with the port down there, under the place where the throttle axel is, more towards the engine (behind throttle as per the air flow). It is a short piece of metal pipe, about 4-5mm diameter, sticking out of the housing. On the picture you have the rubber pipe connector installed on this pipe and the white plastic line coming out of the rubber connector.

In this set up (vacuum retard throttle and distributor) you have the biggest vacuum after the throttle at idle (throttle closed, suction from engine). As throttle opens, vacuum gets lower and releases retard from distributor that advances the timing. Idle = high vacuum = retarded timing.

Sorry if I am messing anythign up...

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