2 barrel dual carb vs 4barrel single carb

[Foundwaldo1]

My question is quite simple. Would a dual 2 barrel carb put out more power than a 4 barrel single carb. I was reading up on some classic cars and saw many with dual carbs and then some with single 4 barrel. Is it all just preference?

[vgames33]

Two smaller carbs likely flow more CFMs than one large single unit, but if I recall, twins are a pain to set up properly. I'd assume they provide a little smoother throttle response as well as better fuel mixing due to manifold design, but I'm an EFI guy so I can't say for sure.

[oldblu65]

There might be a small increase in power but that would be negated by the cost of the new components and the difficulty of properly setting up the dual carburetor configuration . You would likely need the help of an experienced " performance oriented " mechanic to get the system to work efficiently ? The only real world gain I think you would get would be cosmetic as this setup would likely impress some people when you open your hood . Just my $0.02 - " Worth every penny that you paid for it " ! Good luck and keep us updated on which direction you choose to go ! P.S. -I agree with vgames33 that EFI would be the way to go ! Much better efficiency than a carburetor with better MPG as well ! The cost would be similar to the dual carburetor setup and a much better choice in the long run .

[MagicRat]

It's difficult to say one is better than the other. It mostly depends on the design of the carbs being compared the engine tuning, and the intake manifold design. Some carbs have less airflow, others have less-efficient fuel delivery systems, some differ in application.

However, for the sake of argument, lets say the 2 bbl and 4bbl cars have the same airflow, mixture efficiency and overall design per barrel.

Functionally, almost all 4 bbl carbs and many (but not all) 2bbls are "progressive". There are 1 or 2 primary barrels that open under moderate use and 1 or 2 secondary barrels that open under higher loads. This progression improves fuel economy and engine responsiveness without sacrificing power.

Some 2 barrel carbs are not progressive, in that both barrels open at the same time. If you use two of these, then you can easily overwhelm an engine where it gets too much air at one time and a subsequent loss of vacuum signal. Such a set up would produce poor fuel economy and would bog/stall if you gave it too much gas pedal at lower revs. Therefore, almost all 4 bbls would be better than this 2 bbl set-up due to their progressive nature.

So.... comparing progressive carbs.... all other things equal, there is no difference between a 4 bbl and dual 2 bbl set-up, except for the following

1. A dual 2 bbl set up allows you to make an intake manifold with more even fuel distribution for inline engines (not V or opposed engines), because you have an opportunity to make for more even-length intake runners. When tuned properly, this gives the dual 2 bbl a slight edge in power and economy.

2. A 4 bbl carb never needs synchronizing. Dual carbs need to be adjusted and synchronized so both deliver the same amount of fuel/air mixture, so maintenance is slightly increased.

3. A 4 bbl carb is more compact and would have a more simple air filter system and fuel line design, so it would fit better in tight engine compartments.