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Discussion Starter #1
Since I'm about to go and get my engine replaced and beefed up a little, I was wondering about dual carb setups.
I've seen dual quad applications for 302's but I wonder if there is any performance benefit over a single 4bbl carb, or that it just looks awsome?
Anyone here who knows about these things?
When there's no real performance gain I tend to go by single carb in case I'll build me a working ram-air flapper setup someday.

Thanks,
Matthijs
 

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I can't imagine a Holley 750 not being big enough to handle the flow for your 302... probably a 600 cfm unit would be more than adequate. I wouldn't spend the dough on the intake necessary or the matched carbs... not to mention the setting up of such a thing.

I think the tendency is for people to be over carbureted.

I have a 302 in my car with a LOT of cam and ported heads, I'm runnning a single 780cfm Holley, vacuum secondaries, single pumper. Works just fine.

Over carburation can kill your low end throttle response... especially if your primaries are so big that air velocity is low. Keep your primary bores smaller, keep the airflow velocities a little higher, and you'll be a lot happier with your low end throttle response.

Ron.
 

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Discussion Starter #3
Thanks Ron, single carb it will be. I just wanted to have asked and know about it than be ignorant.
When I saw it I thought it looked cool, but then the question popped up what use it would be and esp. what carbs should be bolted on. I've read some other threads about carbs and there seemed to be people having trouble being over carbed, so anyway, it didn't make much sense (although it really is a 289/302 application) but still looked great...

Thanks again (good sidenote about the primairy venturis, wouldn't have thought about that one:rolleyes: )

Cheers!
Matthijs
 

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totally hypothetical

Totally hypothetically, I wonder if 2 carbs with very small venturis would give better part throttle performance and gas mileage than 1 bigger carb.

Like 2 250-300 CFM carbs instead of a single 500 - 600?
 

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dual carbs

Matthijs,
I have a 351 windsor with medium performance cam and all the associated performance mods from edelbrock intake to comp cams adjustable valve train, to headers and 2 1/2 inch duals. The most important thing to remember when building the engine is that the components match. I have tried 3 different carbs on my 351, and I have settled on the Road Demon 625. Plenty of low end throttle response and screams to 5000 RPM. To many people can't help getting caught in the "bigger is better" mentality. A great many street performance motors are over carbureted or over cammed. This kills low end throttle so much that the car is too slow for the gains in high RPM range to even make a difference. On a small block motor, twin carbs are best suited for high rpm race engines that have big stall converters or 4 speeds.
I am currently building a 428 motor for my cougar, and I am planning on using dual carbs. But even on a medium performance 428 I am only using two 600 CFM holley's and setting up the linkage to use the carbs progressively, so that I do not over carb and kill the low end torque. I hope all my rambling helps you!
Paul G.
69 XR7 Convertible
 

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2 small carbs

Neal,
Conceptually two small carbs with small venturi might sound good, but it would be hard to tune and synchronize the two carbs. I would think that most of the advantage of the two smaller venturi would be lost in the tuning. Most dyno tests show that better performance can be gained from a good matched cam, intake, single 4 barrel, and free flowing exhaust. The only reason I am going to a dual quad on my 428 motor is that it will look really cool at car shows and cruises. When is the last time you saw a 428 dual quad cougar convertible? I probably could have gotten better performance with a blue thunder or edelbrock RPM manifold and single Holley or Demon carb, but I'm going after the "wow" factor as well.
Paul G.
69 XR7 Convertible
 

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carbs

You guys looking at multipul carb setups, don't forget about the tri-power or three duece setups. They look awesome, but they also can be a nightmare to tune.

:xoli: :xoli: :xoli:
 

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Dual carbs

Dual carbs look great and can be made to perform as intended.

427 Tunnel port dual 660's on a single plane intake
 

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Discussion Starter #12
Hmm, sounds like not everybody agrees on this subject. I must say I like the idea of using 2 carbs progressively, especially since I'm planning on a [email protected] cam (and high stall converter) so it would be kind of neat to have a carb setup for idle and lower rpms and have the second one come in when torque is needed. Besides that it sounds like a real challenge to me to go and tune 2 carbs.
Now I'm wondering, when it sais 650 CFM for example, does that mean the carb is capable of letting a maximum of 650 cubic feet per minute pass, or am I completely wrong here.
If so, wouldn't it be possible to calculate the carb needed for certain rpms using the engine displacement and rpm (assuming 2 revs would pump through the eng. displacement)?
That would be really nice if it would work that way.
Anybody who knows?

Thanks,
Matthijs
 

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Re: Dual carbs

badcat427 said:
Dual carbs look great and can be made to perform as intended.

427 Tunnel port dual 660's on a single plane intake
Cool motor!!

Where can I get one at?


:1zhelp:
 
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