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4bbl to 2bbl

This is a discussion on 4bbl to 2bbl within the Performance forums, part of the General Discussion category; Hi all, I have a 1978 Chevy C1500 4x4 with a 400 sm blk and an automatic trany. This ol ...

  1. #1
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    4bbl to 2bbl


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    Hi all, I have a 1978 Chevy C1500 4x4 with a 400 sm blk and an automatic trany. This ol gal has a gas guzzling Q-Jet for a carb. My delima is that I would like to reduce the carburetion to a 2bbl with an auto choke. Its my understanding that this can be done with an adapter plate thus eliminating the need for changing the intake manifold. Basically I'm looking for some advice on which 2bbl carb would be best for this task. Any and all advice is greatly appreciated.
    Many thanks in advance.

  2. #2
    Hey watch this Colby 04's Avatar
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    Re: 4bbl to 2bbl

    The dual jet(2 barrel version of the quadrajet) probably won't save you much on gas. The secondaries only open if you get into it right? I didn't notice any huge difference in mileage when I went from a dual jet to a cammed, edelbrock 600...

  3. #3
    GMC RULZZ NEUMANNZZ's Avatar
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    Re: 4bbl to 2bbl

    when was the last time the carb was rebuilt? is gas leaking out of the throttle shafts?
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


  4. #4
    Moe Howard
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    Re: 4bbl to 2bbl

    Quote Originally Posted by gjwizard
    Hi all, I have a 1978 Chevy C1500 4x4 with a 400 sm blk and an automatic trany. This ol gal has a gas guzzling Q-Jet for a carb. My delima is that I would like to reduce the carburetion to a 2bbl with an auto choke. Its my understanding that this can be done with an adapter plate thus eliminating the need for changing the intake manifold. Basically I'm looking for some advice on which 2bbl carb would be best for this task. Any and all advice is greatly appreciated.
    Many thanks in advance.
    Switching to a 2bbl on that heavy truck would likely DECREASE your fuel economy by forcing the engine to work harder to accelerate. Don't do it..if you need to save gas, buy a elcheapo used POS 4 banger..

  5. #5
    Banned 932500's Avatar
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    Re: 4bbl to 2bbl

    you will be much better off rebuilding the current carb instead of running a 2 barrell. look at you primerys in the front. If you run on them alone you are anly pullig in around 250 CFM, Unless you run into the 4 barrel alot you will get better mileage out af a soread bore lie the one you have

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