why does my holley 94 have two barrels, two butterflies?

[hueyhoolihan]

all my research shows that both barrels of a holley 94 (1941 ford oem carb) open at the same time, at the same rate, and have the same sized jets and feed into the same large common area inside the intake manifold.

so what makes one a "primary" barrel and the other one a "secondary", as they are often described? and, if queried about the difference between the two barrels i've been given hints that they open at different rates, which would make sense, if they did...but they don't.

[tubman]

They are both "primary barrels and are designed to open at the same time. Your car has what is called a "dual-plane" manifold where each throttle "barrel" feeds 4 cylinders. The manifold is designed to distribute the fuel mixture to each cylinder in the most efficient way determined by the engine's firing order. Take a good look at your intake manifold and you should be able to follow the eight separate paths the fuel takes.

Progressive two barrels are a much later development than what is on your Ford. I think they were developed by Weber. They are generally used on 4 cylinder engines and are rarely (if ever) seen on eight cylinder engines.

[38 coupe]

The Stromberg carburetors (48, 97, and 81) and the Chander-Groves / Holley / Ford carburetors are two barrel carburetors without a primary and secondary barrel. As you expect both barrels work at the same time.


There are some progressive two barrel carburetors, typically on small displacement engine of European design, most commonly made by Weber. Do an image search for a Weber 32/36.

[hueyhoolihan]

thanks guys, big help!

okay...that makes sense. so references to primary and secondary are without merit
WRT my carb. inasmuch as they both work the same.

and would it be fair to say that the intake manifold accepts the fuel/air mixture from the carb's two barrels into one of two completely separate sections of the intake manifold that in turn directs the mixture to each of the four cylinders in each bank? such that if it were possible (but it's not) to close one butterfly and leave the other open, the engine would be getting fuel to only one bank of four cylinders and none at all to the other?

[tubman]

Correct. Except that it wouldn't be "one bank", but two cylinders on each bank.

[hueyhoolihan]

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Originally Posted by tubman

Correct. Except that it wouldn't be "one bank", but two cylinders on each bank.

ah!!! so the intake manifold's runners from each of the barrels lay transversely across the block. that never occurred to me, thanks.

are they four rearmost cylinders and the four frontmost cylinders are do they alternate?

BTW, i really do appreciate the knowledge expressed here. these kinds of details to me are what make diagnosing problems much less time consuming. especially so when presented in a relaxed and pleasant manner.

[alchemy]

I think the terms of primary and secondary that you’ve heard about are referring to a three carb setup. The center carb is the primary and the two outer carbs are secondaries.

[Mart]

One side does the end cylinders on one side and the middle cylinders on the other side.
The other side does the remainder.
I'd have to check but I think each side does every other cylinder in the firing order.

[hueyhoolihan]

Originally Posted by Mart

One side does the end cylinders on one side and the middle cylinders on the other side.
The other side does the remainder.
I'd have to check but I think each side does every other cylinder in the firing order.

so, it's not so straightforward...understood. thanks.