Not totally accurate. The secondary air door has an impact on air flow only IF they are adjusted a certain way. While we all understand the function of the secondary air doors (well, maybe some do and some don't) this is the first time I have heard anyone describe the Carters as vacuum secondary carbs. There are a few AFBs that actually used a vacuum pod to operate the secondaries and there are AFBs without secondary air doors.Twist it any way you want to make an argument, but the secondary throttle plates are opened by direct linkage from the primaries (for the vast majority of Carters) and the air doors are above the boosters on most models so that they are as much an enrichment device as they are an air flow control device. The air doors have an impact on the secondaries' operation, but they do not control them. Primary control rests with the linkage and linkage alone.

Mopar's Carters were not vacuum secondary carbs.

I said they are considered vacuum secondary carbs because the secondaries function off of engine demand and not strictly off of the throttle plate butterflies. Twist however you want but look them up on Summit or Jegs and see if they are listed as mechanical or vacuum secondary carbs. You could also try pointing out where the secondary accelerator pump squirters are on those carbs.

You mean like this ?

So you use sales ads for your technical information? That helps explain your opinion on this.

And I have no idea what you are trying to say about the pump squirters. Did you read that in an advertisement, too?

Bottom line; the secondary air door is not essential to the operation of the secondaries. It can be an asset and certainly helps in some applications but is not an absolute necessity.

Straight out of the Carter manual for the TQ

Mechanical secondaries with a variable venturi feature. Good points, straight from Carter and not from a sales brochure.

Venturi: A Venturi is a system for speeding the flow of the fluid, by constricting it in a cone shaped tube. In the restriction the fluid must increase its velocity reducing its pressure and producing a partial vacuum. As the fluid leaves the constriction, its pressure increases back to the ambient or pipe level.

A venturi DOES NOT control the secondary operation. It aids it.

Thank you.

it says : "image not found" on my screen.

I have a Street Demon on my mild 440. I went to the chassis dyno guy on Friday to have the carb tuned after a recent engine build. He refused to do the job until I put a Holley on. I guess he doesn't like to take the time to disassemble the carb to change jets. Or he doesn't understand metering rod carbs. Either way, i guess I am back to dialing it in some old fashioned way.
On the prior engine a different dyno guy was ok with the Street Demon but then he changed metering rods to avoid changing the jet! It was close enough.

I wish I knew of a chassis dyno here in town. I guess it's possible there's one I don't know of but never heard of one and we're not that big. Also isn't a street demon a Holley? I guess he meant same design not "owned by".

Larry,

If you score a 9800 series TQ I will set it up for you. The attached electric choke takes care of running this beast with any intake you chose.

Anyways, they are out there, I see them occasionally pop up on eBag...not too often, but they can be found.

I have a 9801and a 9811

Read the first and second sentence in snipers attachment again. That is what I'm saying. You can't open those secondaries mechanically without some sort of restriction to delay the intake of additional air or you need a secondary accelerator pump shot to prevent a huge backfire and most likely stalling the engine. In other words, vacuum secondary carbs allow the intake of extra air and fuel as the engine demands it, not as a function of the mechanical linkage alone. Block that secondary air valve fully open and then tell us how those mechanical secondaries work.
I don't know why you want to argue this point, it's really useless and unproductive, so whatever, I'm done.

My last post on this was 6 DAYS AGO. You resurrect this, reiterate your point, and then tell me it's not worth arguing about.

And by the way, you're wrong.

I used to run a TQ and a Holley Spread Bore on my 340. Swapped them as I felt. I also used square bores as I wanted too.

For me the TQ was temperamental but when it ran it ran better then a Holley. The Holley was consistent.

I never noticed a difference in the performance for the spread bore vs square bore when I swapped them out. It always seemed to be a matter of tuning and design.

I would say for me the Carter's gave more power but since they were metered with pistons and springs they tended to "hang" and be more temperamental.

If you like that spread bore sound but holley tuning simplicity. Run a Holley Spread bore. I was just at a swap meet and there must have be 10 of them for sale for $50 each or less.

Holley owns Demon now, but the only thing in common is the secondary jets.

I was just about to ask that.

One thing I really like about the new design factors of Demon are the large bowls helping with starts after sitting for several days. Damn 10% ethanol. I get about three days parked and after that have to pour gas down carb. Would rather not have to install another pump.

One MAJOR improvement over the Thermoquads is that there is no gasket at the bottom of the fuel bowl.