Thermoquad- do I need that part?

[Sonny]

What is this tan contraption on the lower right side that looks like a top? Do I need it? It’s off a 1978 truck 440. Notice the awesome rebuild job from National Carburetors! It was green and black when I gave it to them.

 

[Darter6]

That is called a dash pot. It is most often found on stick shift cars/trucks. It allows the throttle plates to close slowly to the idle position. I think it was to keep it from stalling if you removed you foot off the gas pedal quickly. Do you need it ? Can't say. My truck is a automatic and it don't have one.

 

[tonysrt]

It looks good but more importantly is how it runs. Let us know, so if happy with results you can recommend him.

 

[SublimeSixpack]

A mini shock absorber for your throttle.

 

[Sonny]

A mini shock absorber for your throttle.

I’m going to use a 727 automatic. I assume it was vacuum operated?

 

[SublimeSixpack]

I’m going to use a 727 automatic. I assume it was vacuum operated?

None of my Thermoquads have this dashpot but near as I can tell from your photo images I'd say your's is mechanical in how it works.

 

[rumblefish360]

Vacuum operated? I haven’t seen one vacuum operated. I guess it could be. It should have an electrical connection. The device shuts the carb butterflies closed when off to prevent run on.

 

[rumblefish360]

Oh! How much for the rebuild?

 

[SublimeSixpack]

It's there to cushion the closing of the throttle once the driver lets up on the accel. pedal.
I think the mindset was that it would reduce emissions.

 

[Sonny]

Oh! How much for the rebuild?

$225.

 

[Darter6]

Smokin' good price. I had Harms do mine and it was around $425 or so. I'm not complaining I am more than happy with their work.

 

[idrivemopar]

That is actually the fast idle solonoid for cars equipped with air conditioning. Also the little lever hanging down on the primary linkage on the driver side is for cruise control.

 

[idrivemopar]

Here is what the older style looks like, electrically activated, unlike yours which appears to be vacuum activated, and if that is the case, remove it, and if you don't have AC, you can remove it. This is the thermoquad on my 73 340 and you may notice it has the float bowl vent (hose attached and lever on throttle) as well where the post 76 ones I believe didn't have it.

 

[SublimeSixpack]

Sonny, was that device on your carb when you sent it in for rebuild, or did the rebuilder add it?
I know some came with an electrically energized solenoid to bump up the RPM when the A/C was turned on. But the one you have pictured appears to be a mechanical type dashpot. I say this because I see no solenoid, or vacuum connection for it to be activated.
Would you be willing to take a close up photo or two of it so we can see if indeed there is a vacuum fitting anywhere on it?
I'm really curious about this piece.

 

[Sonny]

It was on the motor when I got it. Appears to have a hollow tube on the front end that had a vacuum cap on it before the rebuild.

 

[SublimeSixpack]

Thanks, I see now that it is vacuum activated. Not a dashpot. I was incorrect in my earlier posts.

 

[rumblefish360]

We’re all here to help and/or learn something!

 

[383man]

Most dashpots are hydraulic but I have seen some that were vacuum operated. I have also seen them that were AC idle up units. The vacuum dashpot and AC idle up unit look close to the same. Easy way to tell is see what it does when you put manifold vacuum to it. If its an AC idle up unit it will extend some when vacuum is applied to raise the idle. If its a dashpot it will pull in when vacuum is applied as they will go out when the vacuum drops when stepping on the gas and when you let off the gas and vacuum will be stronger and it will slowly pull the dashpot back in for a slow return to idle. Funny as Ford actually used dashpots on auto trans equipped cars and Mopar used them on stick shift manual trans cars. Mopar used it to reduce emissions on decell as did Ford but Ford also wanted to help so the car would not stall with the auto trans and a quick release of the gas pedal in gear. Myself I have not seen one on a Thermoquad before. Just test it with vacuum to it and see what it does as "idrivemopar" may be right about it and it may be for an AC idle up speed as it will extend out with vacuum if it is. Ron

 

[pentahead]

Very common on trucks