Thermoquad Vacuum Port Questions

77newyorker440

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Good Afternoon,
As shown in the picture below, this new tq has quite a few vacuum ports. Which one is for vacuum advance, and what are the others for? Including the bizarre one on the 45 degree angle. I know the large on in the middle is for the PCV.
Thanks,
77newyorker440

20220111_165558.jpg
 

Boydsdodge

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This is from the 76 Service manual. There is also a good source you should look up called the Thermoquad guide by Vanth
IMG_0661.jpg
 

Boydsdodge

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If you bypass the OSAC valve, that port will go directly to your Vacuum advance on distributor. Which is what I would do.
 

thethee

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I found the following online from the thermoquad guide. I disconnected mine and it's been running fine.

Idle Enrichment (IE) system:75-81. This is a driveability enhancement. It supplements the choke function by allowing an even richer mixture during the warm up period to improve driveability. This will appear as a small attachment on the front bowl cover that has a vacuum port that connects to a coolant temperature sensor (CCIE), then to manifold vacuum with bleed. It will also be plumbed into the EGR delay timing system.
 

70bigblockdodge

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Ported vacuum to vacuum advance, nothing else.
PCV to PCValve.
In right rear to vacuum pot for choke pull off and air door dampener.
If your still using the air cleaner heat stove you would connect that(you should not have it connected with headers).
You can connect the bowl vent to purge canister, but I would not connect purge canister to base of carb.
Plug everything else.
 

70bigblockdodge

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It is strictly a emission connection to draw a vacuum on the purge canister to clean out the vapors and in turn vent the tank/no positive pressure in the tank.
The tank will vent through the purge canister and through the float bowl and the vents in air cleaner, so it will function much the same as a late 60s vent to atmosphere. The orifice regulated vacuum on the base is to inconsistent of a fuel, air, or just plain vacuum leak to allow for a very consistent idle mixture.
 

70bigblockdodge

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New cars with fuel injection can vary mixtures constantly and adjust idle air volume. This allows a purge system to work well
 

thethee

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That makes a lot of sense, hadn't thought about it like that. I'm gonna disconnect mine this weekend. :)
 

70bigblockdodge

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That makes a lot of sense, hadn't thought about it like that. I'm gonna disconnect mine this weekend. :)
I am not anti emissions, but some of those systems were designed to fix a certain parameter in the government or California emissions guide lines. They may have done that very well back in the day. Unless you are driving your antique car 10-15k a year and another 5-10k of the other owners of those cars start using them like that, it really will make no difference in air quality. Tuned up, not worn out, properly running will outweigh these oddity emission correction devices.
 

thethee

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Oh I am not anti emmissions either so I won't just yank it out, but I am pro trying things that might make it run better and a vacuum leak is a very real possibility.
Also, if capping it off improves things, it likely was already venting to the atmopshere. The vacuum gauge will tell.
 

CBODY67

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Personally, it hurts NOTHING to have the carbon canister hooked up and worrking as designed. Keeps that "fuel smell" out of the engine compartment, too!

The CCIE (Coolant Controlled Idle Enrichment) is a patch system (to me) for a very lean-calibrated carb to get through the cold start with a degree of reliability in performance. Earlier models didn't have it. Might also be one of those systems which makes very little difference in how things operate, EXCEPT when the exhaust is going into a meter to measure things, too, Yes, there is probably a thermo-vacuum switch which runs it, too, as it is related to coolant temperature below a certain level. Just as there is probably a TVS to run the EGR valve, too, to keep it closed below a certain coolant temp.

The OSAC is another patch of sorts for a certain operating situation. As I recall, it can be deleted as it was not on earlier vehicles, either.

Please tell us what type of vehicle the carb is going on and why you needed a new to you carb for it? Just curious.

Enjoy!
CBODY67
 

77newyorker440

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Putting on a Autolite C6090 reman TQ because I had to remove the old lean burn carb as the lean burn failed, and using the reman until I can have Dana set up the original card for non-lean-burn use
 
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