Dist. vacuum advance, retard, ported, manifold?, Anybody know the real story? Options

[JPA914]

I'd like to test the vacuum canister on my 1974 2.0. It just has the one line going to the TB, the other vacuum port is open to the atmosphere. TB has only one port, the other is blocked off for my year model. Now, from all I've heard, this is a retard ONLY setup with no vacuum advance.

However, if I'm understanding correctly how vacuum retard works, I think the canister should be connected to a ported vacuum on the TB. And a ported vacuum source is one that is above the closed throttle plate, so that timing is not advanced at idle (no vacuum above the plate) but advanced at part throttle (source is now below the slightly open plate, creating vacuum).

The problem with this model is that the only vacuum port on the TB is clearly below the closed throttle plate. This would be a manifold vacuum source, usually used for advance only, as the advance would be highest at idle (most vacuum) and less and less as the throttle is opened further. There is no "ported" source. Anybody know if this really is a "retard only" system and, if so, how it's supposed to work? I probably need to know that before I test it (IMG:style_emoticons/default/smile.gif)