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Ignition Distributor which Vacuum Port?

1772 Views 5 Replies 3 Participants Last post by  willy3oy
I am following the Vacuum diagram for my 500 SEC (with 500SL Engine) and I need to run a line to the Ignition Distributor to advance the timing. My distributor has 2 vacuum ports, both of which are currently connected to the vacuum system and are almost certainly going to the wrong places. Could someone please shed some light on whether I should be using the lower or upper vacuum port on the distributor as shown in my photo. And what is the difference between the 2 ports? I have done a lengthy search but cannot find any mention of this. Thanks

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Thank you both for the replies.

I am following the vacuum diagram for my car and there is only one mention of the Ignition Distributor in the entire system. And that is the intake manifold (via a strainer valve) connects to the Ignition Distributor Advance.

I suspect the current connections by the PO are useless. The top port (advance) is connected to the Vacuum Switchover Valve by the throttle body. The lower port (retard) is connected to the lower chamber of the Warm Up Regulator. Doesn't make sense to me.

With this being the case, can I safely disregard the lower port on the distributor do you think?
That's a good point but the vacuum systems (within the engine compartment) are the same for both cars.

This is the 500 SEC system - it doesn't show the EGR part but it is the same as for the 500SL


And this is the 500 SL System:


Both just show the vacuum line connecting from the manifold - via the strainer - to the Ignition Distributor Advance.
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