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  1. #1

    Default Upgrading a 2 barrel Rochester to a 4 barrel

    I have a 3 litre GM OMC with a 2 barrel Rochester Carborator and I am looking to find out if anyone has converted their engine to a 4 barrel Carborator in order to increase horsepower. Any thoughts or suggestions ????

    I was thinking of a 4 barrel of approx. 490 CFM for this 180 cubic inch engine. Too much?, will it flood?, will I gain horsepower?

    other alternatives?

  2. #2
    Moderator Bondo's Avatar
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    Default Re: Upgrading a 2 barrel Rochester to a 4 barrel

    will I gain horsepower?

    other alternatives?
    Nope,...

    Not really....
    Any Grease is Better,..... Than No Grease at All.......

  3. #3
    Rear Admiral Howard Sterndrive's Avatar
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    Default Re: Upgrading a 2 barrel Rochester to a 4 barrel

    4BBL would be too much
    Baba-buoy.

  4. #4
    Commander zbnutcase's Avatar
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    Default Re: Upgrading a 2 barrel Rochester to a 4 barrel

    350 cfm Holley marine carb is the max I would do on a stock 3.0-if I bothered at all. Only pencils out if you need a new carb anyway.
    You meet the nicest people at the American Legion.
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  5. #5
    Commander bifflefan's Avatar
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    Default Re: Upgrading a 2 barrel Rochester to a 4 barrel

    Id call that a drowning, not an upgrade.
    Upgrades make things better, and that wont.
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  6. #6
    Chief Petty Officer
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    Default Re: Upgrading a 2 barrel Rochester to a 4 barrel

    Yup, probably make more sense to put a 1 bbl carb on it than a 4. But that's a down grade too.

  7. #7
    Commander 45Auto's Avatar
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    Default Re: Upgrading a 2 barrel Rochester to a 4 barrel

    As others have said, a 4 barrel carb will not make any difference on your 3.0L. Any internal combustion engine is a pump, it sucks air in and pushes exhaust gases out. The carburetor on your engine is NOT the choke point that is restricting the flow through your engine. Essentially the same carburetor is used on the 4.3L, the 5.0L, and the 5.7L. One of the members here just replaced the 2 barrel on his 5.0L with a 4 barrel, you can see his results on this thread:

    http://forums.iboats.com/non-repair-i-o-inboards/how-much-hp-would-gained-adding-4bbl-5-0l-volvo-gl-vortec-396275.html

    If you don't feel like reading the thread, I can summarize it for you: it made no difference at all.

    He was also using a manifold designed for a 4 barrel, not some hodge-podge of adapters like you would be forced to use on the 3.0L.
    Any opinions expressed above are worth exactly what you paid for them!

  8. #8

    Smile Re: Upgrading a 2 barrel Rochester to a 4 barrel

    Well I guess I have my answer.
    Thank's guys.
    I just posted my question this morning and now I have a whole lot of info.
    Thanks also for the thread refferal.
    So, to better be able to do all the skiing with a boat full of people I guess I should invest in another prop rather than carb since it isn't going to give me any power increase.

    Yes, thank you all again.

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