Need help from Carter Thermoquad experts

[HD539]

Attached is a picture of my thermoquad carburetor for my 71 340 duster. The tube with the red cap is what I have a question about. Does anything attach here ( hose or whatever). I’m very familiar with AVS carbs but am new to the thermoquad.

Please advise, thank you.

 

[remytherat]

An evap canister if you have one. If you don’t, it is completely unnecessary and you should leave it capped.

 

[340wedge]

Attached is a picture of my thermoquad carburetor for my 71 340 duster. The tube with the red cap is what I have a question about. Does anything attach here ( hose or whatever). I’m very familiar with AVS carbs but am new to the thermoquad.

Please advise, thank you.

View attachment 1716416170

It's a vent and goes to the breather on the valve cover connected by a hose.

 

[remytherat]

goes to the breather on the valve cover connected by a hose.

Not true.

 

[340wedge]

Then what does it go too? I believe it goes to this, (color should be black not natural steel)

 

[GTX JOHN]

We simply leave it uncapped on all our race car.
We have never encountered a problem.

 

[LO23M8B]

Uncapped is good. I don't think I would plug a vent.

 

[remytherat]

We simply leave it uncapped on all our race car.
We have never encountered a problem.

I tried leaving it uncapped on my street car and what I found is that when it was warmed up, I would get a strong raw gas smell upon letting off the pedal.

The other three vents are plenty. On a race car, sure.

 

[RustyRatRod]

Since there are three HUGE bowl vents on the carburetor, there's no need to leave that vent tube uncapped. Cap it.

 

[Bewy]

^^^This.

 

[Bewy]

That carb looks in beautiful, original condition!

 

[jumper34]

It was the beginnig of the emissions reduction in 71, and it goes to the breather cap, as mentioned above. There should be one that goes back to the gas tank that connects to the smaller inlet in addition to the bigger port connecting to the air cleaner.

 

[Dartswinger70]

Yeah I wouldn't plug a vent it may cause issues in the fuel bowl think of lifting water out of a glass by putting your finger over the end of a straw

 

[HD539]

Thanks everyone, I have things to consider. I’m just about done with the car and had that as a question. The red cap was only meant to identify which vent tube I was referring to. Once again thanks.

 

[Bewy]

As stated already, carb has three large vents, a fourth is not needed & can be capped. Holleys 4 bbls only have TWO vents...& do just fine.