Thermostat Vacuum Thing

[badazz68stang]

i have a 68 289 motor that has a weird vacum set-up. The distributor has two vacum lines and on top of the thermostat housing there is a thing with three vacum ports also, i kno ford did this for emissions reasons, but what i am askin is, is anyone familiar with this setup?, if so how do i run the lines
(to and from). thanks guys.

 

[geostang351]

I believe the "thermostat" housing you are refering to, is located at the back of the intake manifold behind the carb correct? If so, this is for vacum for hooking up to the Automatic tranny for shifting and use for the brake booster that is equiped with power brakes. The actual thermostat is located at the front of the manifold slightly off set to the right with a singal wire attached.

So the distributor that is hooked up to the thermostat is actually hooked up to the vacuum fo the manifold.

 

[likesoldjunk]

Your description is a little foggy, and you've got us guessing, but here's
a little input:

- If your distributer solenoid has two ports, the one on the 'nose' goes
to the 'Spark Port' on the carburator that is above your butterflys. On
a Holley, that port is halfway up the front metering block.

The one on the side of the distributer goes to manifold vacum, which
could be on the botom of the carb, or somewhere on the manifold.

- I think the gaget on the thermostat housing you are refering to is a
temperature actuated switch that gets in the way of the two lines above
to give you more vacume advance (to get higher idle) when the engine
is cold. If you have converted to manual choke, you probably don't
need this anymore.

If you want to keep it, and no one has come up with an answer by the
end of the day, I can look up the proper line routing tonight.

 

[66HertzClone]

I can't tell you which way to connect the hoses, but the switch is called a "ported vacuum switch". It is designed to turn on or off depending upon design vacuum from the vacuum source, depending upon engine temps. If your dizzy has two vacuum ports it might be for the vacuum advance. Sometimes these were used to raise idle speed if the coolant temp went above normal position, it allows the second vacuum chamber to advance the timing, thus increasing idle speed.

These were also used for EGR valves and sometimes the flap in the snorkel of the original air cleaner housings.

You could test it by using a vacuum gauge to see if it allows vacuum thru it cold or when hot, I don't believe it would make any difference which way the hoses connect if it has two posts, those with three it would make a difference.

I hope this helps, Jeff

 

[D.Hearne]

The dual chamber vacuum canister on the distributor is a combination advance/retard unit. The front (advance) nipple is connected to ported vaccum, the rear (retard) to manifold, via the vacuum switch.