What carb size mopar 340.

[540HemiCuda]

You do realize that the choke is manually controlled and often does not need to totally seal the venturies while the air door must be able to respond on it's own hence the basic design difference. But is it your position that neither the choke nor the secondary air valve exerts any more pull on the boosters by resisting air flow? If so, you are just plain wrong.

And again, if the air door is not designed to enrichen the secondary's opening point, why don't double pumpers have them, too? ONLY mechanical secondary carbs with no other means to add fuel at that point have them. Why is that?

And your quote does nothing to sway the argument either way.

Here is what AI says: '
The air door, or air valve, on mechanical secondary carburetors (specifically Air Valve Secondary or AVS type) serves to gradually open against spring pressure, controlling airflow and creating a sufficient air velocity to draw fuel from the secondary boosters. This system prevents a lean stumble or "bog" when you stomp on the accelerator at low RPMs, ensuring smooth power delivery by allowing the carb to only add fuel when the engine demands it through sufficient airflow.

The air valve's position controls the airflow through the secondary venturi, creating the necessary velocity to generate a fuel signal from the secondary boosters. Without this system, the secondary throttle plates would open too quickly, causing too much air to enter without enough fuel, resulting in a lean condition or a "bog" '

Or this from a carburetor shop:
'Even if the throttle plates open fully, the secondaries won’t deliver extra fuel unless enough air velocity flows through the secondary side to push open that air door. This prevents bogging or lean conditions when stomping the throttle at low RPMs.
As the air valve opens due to increasing airflow, it activates the fuel metering rods and jets in the secondary side.'

Lots more information about this if you chose to do a search.

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[Xcudame]

Find a good used Thermoquad and rebuild it. Can't find one, get a Holley Street Demon.
@Chryco Psycho is on the money, 2x the cubic inch of the engine.

 

[Litchkar]

I don't know what parts manual you are using, but it is INCORRECT.

And I am not going by anything other than 55+ years of personal experience. Starting in 1972, I have had over two dozen Mopars, sometimes as many as 4 at once. Some stock, some modified. I can list them off for you if you would like. I am now down to just one, a '70 HemiCuda with a 540" Hemi which I built myself like all my engines. And just to throw one last point on my resume; I built a '71 GTX in 2000 (which still had it's original Carter AVS with mechanical secondaries by the way) and it was awarded 95 points out of 100 at the 2001 Mopar Nationals which earned it O.E. Certifed status. So, don't accuse me of using anything other than personal experience especially when you so obviously lack that yourself.

Have you never heard of the Carter AVS? Or the Carter Thermoquad? Both are mechanical secondary carbs, and were standard equipment on just all high performance Chrysler single four barrel applications. And before those, the standard four barrel carbs were the Carter WCFB and the AFB both of which are also, mechanical secondary carbs.

And since you brought up AI, even AI knows that you are incorrect. Google up the carb application for a hi performance 340, 383, or 440. Or you can go to a source like Mopar Muscle magazine where this excerpt on Mopar carbs came from:

'The most common four-barrel carb found on Chryslers during the '60s era were manufactured by Carter and came in two specific designs: the AFB (Aluminum Four Barrel) and the AVS (Air Valve Secondary). From a distance, the two look virtually identical; both are box-like in shape and use a quadrant of evenly or almost evenly sized barrels when viewed from the bottom.

After the WCFB was discontinued, the single AFB was the standard carb on Chrysler performance models until the debut of the AVS in 1968. The specific date code and four-digit part number on both the AFB and the AVS models are easily visible in front of the passenger-side mounting flange.'

http://[URL]https://www.hotrod.com/how-to/mopp-0111-chrysler-oem-carburetors

[/URL]

Seems EVERYONE (except you) knows what carbs came on most of Mopar's hi performance engines.

.

I don't know what parts manual you are using, but it is INCORRECT.

And I am not going by anything other than 55+ years of personal experience. Starting in 1972, I have had over two dozen Mopars, sometimes as many as 4 at once. Some stock, some modified. I can list them off for you if you would like. I am now down to just one, a '70 HemiCuda with a 540" Hemi which I built myself like all my engines. And just to throw one last point on my resume; I built a '71 GTX in 2000 (which still had it's original Carter AVS with mechanical secondaries by the way) and it was awarded 95 points out of 100 at the 2001 Mopar Nationals which earned it O.E. Certifed status. So, don't accuse me of using anything other than personal experience especially when you so obviously lack that yourself.

Have you never heard of the Carter AVS? Or the Carter Thermoquad? Both are mechanical secondary carbs, and were standard equipment on just all high performance Chrysler single four barrel applications. And before those, the standard four barrel carbs were the Carter WCFB and the AFB both of which are also, mechanical secondary carbs.

And since you brought up AI, even AI knows that you are incorrect. Google up the carb application for a hi performance 340, 383, or 440. Or you can go to a source like Mopar Muscle magazine where this excerpt on Mopar carbs came from:

'The most common four-barrel carb found on Chryslers during the '60s era were manufactured by Carter and came in two specific designs: the AFB (Aluminum Four Barrel) and the AVS (Air Valve Secondary). From a distance, the two look virtually identical; both are box-like in shape and use a quadrant of evenly or almost evenly sized barrels when viewed from the bottom.

After the WCFB was discontinued, the single AFB was the standard carb on Chrysler performance models until the debut of the AVS in 1968. The specific date code and four-digit part number on both the AFB and the AVS models are easily visible in front of the passenger-side mounting flange.'

http://[URL]https://www.hotrod.com/how-to/mopp-0111-chrysler-oem-carburetors

[/URL]

Seems EVERYONE (except you) knows what carbs came on most of Mopar's hi performance engines.

.

I see you are new to the site, being knowledgeable is great, but insulting fellow members is not cool. People use this forum to ask and answer questions, not be belittled. Grow up and show some respect.

 

[Rishi]

He is just being reactive, like my teenage son.

while it may be true the secondaries on the AVS and TQ share a mechanical element with the AFB, I don’t agree they behave like the AFB.

the spring controlled valve improves their tuning as a function of engine demand, and it does so at a very tiny cost in performance, possibly not even measurable. In many ways, the secondary opening speed behaves very similar to the Holley vacuum secondaries.

they’re both right, from some schools of thought. but boys, will be boys.

 

[Ricks72Chlgr440]

He is just being reactive, like my teenage son.

while it may be true the secondaries on the AVS and TQ share a mechanical element with the AFB, I don’t agree they behave like the AFB.

the spring controlled valve improves their tuning as a function of engine demand, and it does so at a very tiny cost in performance, possibly not even measurable. In many ways, the secondary opening speed behaves very similar to the Holley vacuum secondaries.

they’re both right, from some schools of thought. but boys, will be boys.

I my mind I always equated mechanical secondaries with those Holley carbs that had dual squirters. Does not make me correct but that's how I run.

 

[540HemiCuda]

I see you are new to the site, being knowledgeable is great, but insulting fellow members is not cool. People use this forum to ask and answer questions, not be belittled. Grow up and show some respect.

What exactly was an insult? I corrected an obvious mistake and responded to being accused of using AI rather than my experience which I consider an insult. In essence, I disagreed, offered support for my position, and asked a couple of questions that cut directly to the point but went unanswered.

I look at it as a challenge that was met. Successfully.