Thermoquad without vacuum advance port options

[zombezoo]

I recently rebuilt the thermoquad shown below (9097s model). It does not appear to have a vacuum advance port for my distributor. I initially had my distributor connected to the small port (top right in the photo) on the back of the carb before I realized it was a manifold vacuum port. The car would not run right this way. Using a vacuum gauge, I discovered the port in the lower left of the photo did not have vacuum at idle. I have connected my distributor there and the car runs much better.

Does anyone know the difference between this bottom left port in the photo and a proper vacuum advance port?

Trying to determine if I should remove the carb and attempt to add a port to the base plate.

 

[AR67GTX]

A lot of Chryslers were set up to run off ported vacuum. A lot of us prefer to run full time vacuum to the distributor for various reasons. if you prefer ported advance (no vacuum at idle) then stick with the port with no vacuum at idle. They are usually fed from a port slightly above the throttle blades so they don’t start generating vacuum until the throttle is opened, increasing air flow and vacuum suction across the port. Ports that generate vacuum at idle are either fed from vacuum pulled from the manifold below the carb, or from a port in the carb, below the throttle blades. The choke break vacuum canister needs to hook to a full time vacuum port to operate properly.

Ported advance - from above throttle blades
Full time vacuum advance - from below the throttle blades

If you ever decide you want to try running your distributor with full time vacuum advance, you can cut the vacuum hose to the choke break and insert a vacuum “T” and hook your distributor to it.

 

[zombezoo]

When I had the vacuum advance canister hooked to manifold vacuum the vehicle ran horribly. It would barely idle once the vacuum line was reconnected after setting the base timing. I tried adjusting timing from base, messed with it a bunch and could not get it to work well. When I switched to a Port that did not have vacuum at idle the car ran much better. I'm not sure why, maybe there's a problem with my distributor.

 

[AR67GTX]

I don’t know. It kind of defies logic as typically adding advance at idle provides smoother running, cooler engine temps and better mileage. But, sometimes someone will write in with your experience so there must be some exceptions. I know for awhile Ford had some really funky distributors with dual port vacuum advance canisters and thermal vacuum switches that did all sorts of crazy stuff. I don’t think Chrysler got quite that crazy but there may have been some 70s stuff I don’t know about. But if ported vacuum seems to run best on your motor then that’s the way to go.

 

[zombezoo]

To clarify, I'm not asking a ported vs manifold vacuum question. I'm asking what the difference is between the bottom left port in my image above and a proper distributor vacuum port is. I don't want to assume they work the same even though they both have 0 vacuum at idle.

 

[RemCharger]

To clarify, I'm not asking a ported vs manifold vacuum question. I'm asking what the difference is between the bottom left port in my image above and a proper distributor vacuum port is. I don't want to assume they work the same even though they both have 0 vacuum at idle.

That looks like the evap purge port.
Look for a hole above the throttle plate, on the passenger front barrel. That should lead you to the port you seek.

 

[Geoff 2]

Something not making sense with the VA operation.

VA ports use 3/16" tube; the bottom right is 1/4", so not for VA. I doubt you could 'install' a port, as fitting 3/16" tube to the base can be done, but TQs have a rectangular port in the t/bore for ported VA. Getting that shape & getting it at exactly at the correct height relative to the t/blades would be very hard.

I would investigate why MVA is not working? That era carb used MVA to cool the engine if it got too hot. A temp switch switched from the useless PVA to MVA.

More on MVA benefits & the PVA aberration, scroll down to post #6.

www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html

 

[Jonas Nordstrom]

I recently rebuilt the thermoquad shown below (9097s model). It does not appear to have a vacuum advance port for my distributor. I initially had my distributor connected to the small port (top right in the photo) on the back of the carb before I realized it was a manifold vacuum port. The car would not run right this way. Using a vacuum gauge, I discovered the port in the lower left of the photo did not have vacuum at idle. I have connected my distributor there and the car runs much better.

Does anyone know the difference between this bottom left port in the photo and a proper vacuum advance port?

Trying to determine if I should remove the carb and attempt to add a port to the base plate.

View attachment 1522025

As written earlier, the bottom left port is emission stuff. I dont know if you have anything attached to that on the TQ top but best is to add your own ported port.
The TQ ported port can be found on the drivers side.
Drill a hole into the base to the square hole close to the drivers side primary venturi, add the tubing and you are done.
A small slot should be seen in the drivers primary venturi. That is where ported vacuum is taken from. Good luck.

 

[zombezoo]

As written earlier, the bottom left port is emission stuff. I dont know if you have anything attached to that on the TQ top but best is to add your own ported port.
The TQ ported port can be found on the drivers side.
Drill a hole into the base to the square hole close to the drivers side primary venturi, add the tubing and you are done.
A small slot should be seen in the drivers primary venturi. That is where ported vacuum is taken from. Good luck.

View attachment 1525322

Perfect, thanks!