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Old 05-03-2013, 12:59 AM   #1
serge_saati
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Carburetor scoop questions

I want to know what is the purpose of the butterflies on a carburetor scoop. Are they acting like air a choke valve (shutter) or like a suplement throttle plate to control air debit to the carburetor? Or to look like a fuel injection system?

The three round red plates.




And why on some hot rod cars, these butterflies are only 5° open all the time? Why they aren't opened at 90° to increase air debit?

And why some of them are opened while the driver accelerates and close while he releases accelerator? I mean it enrichs the fuel mixture because vacuum increases when he releases accelerator. They are not supposed to stay fixed on a carburated engine? It should not be only the throttle plates inside the carburetors that should open and close with the accelerator?
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Old 05-03-2013, 08:13 PM   #2
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Re: Carburetor scoop questions

It's all for looks. It's for faking guillible non-car people into thinking it has a roots type supercharger (blower).
You can look at the carburetor and see that the individual is not serious about making horsepower. It is an Edelbrock, which is a a rehash of the old carter AFB that Chevrolet abandoned in the mid '60s. It is a reliable carb, and that's about it.
The engine is most likely going in a car that is meant for local car shows and cruise-ins.
If he takes it to the strip, serious racers will laugh at him and point...
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Old 05-03-2013, 08:35 PM   #3
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Re: Carburetor scoop questions

Ok thank you. That's what I thought.

On a carburated car with supercharger like this one:



The scoop's butterflies for a supercharged engine are still fake, right? Do we really need those butterflies?


Some blower scoop doesn't have butterflies like this one:


The butterflies are only for the style to look like a fuel injected car?
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2002 Ford Taurus SE 3.0L OHV (sold)
1998 Ford Windstar LX 3.8L OHV (sold)
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2004 Hyundai Accent GS 1.6L DOHC manual (sold)
1995 Oldsmobile Cutlass Supreme S 3.1L OHV (sold)
2002 Ford Crown Victoria Police Interceptor 4.6L SOHC (sold)

A Windstar without having the check engine light is not a real Windstar.


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Old 05-03-2013, 08:50 PM   #4
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Re: Carburetor scoop questions

Another show car.
What the carbs really need is a large air filter on top.
In this case, not saying that the car is slow (that would be stupid as I don't know anything about the car), but IMO it would be better served by taking that stupid throttle thing off the top.
But hey, it's his car so he can do anything he wants.
If somebody else could chime in that's knowledgeable about these things that would be good.
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Old 05-03-2013, 09:59 PM   #5
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Re: Carburetor scoop questions

They're just for show.
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Old 05-05-2013, 10:30 PM   #6
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Re: Carburetor scoop questions

All these show cars with the butterflies are trying to emulate supercharged, fuel injected drag cars, like this:



Fuel injected induction systems like this need the butterfly valves as throttle control. Any set up with carburetors (even with a supercharger) does not need such butterflies.
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Old 05-05-2013, 10:37 PM   #7
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Re: Carburetor scoop questions

Thank you MagicRat!
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