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Thread: Round Tops vs. Flat Tops - Float Bowl Volume Capacity

  1. #1
    Boat Anchor Repairman Captain Obvious's Avatar
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    Default Round Tops vs. Flat Tops - Float Bowl Volume Capacity

    Upon request, I have measured the fuel capacities of a typical round top and flat top carb. Note that due to shortcuts I took to make the measurements easier, I'm not claiming accuracy to the cc here, but the results should be fairly accurate.

    Here's the round top:





    And here's the flat top:





    The bottom line is that they are close, but it appears that the flat tops have a greater capacity in the float chamber.

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    So what..... a gallon jug will hold more than either. What are we trying to show here?
    Bruce Palmer
    Salem Or
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    Boat Anchor Repairman Captain Obvious's Avatar
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    Hi Bruce,

    I'm sorry, but I'm not sure I understand your question... What we're trying to show here is the volumes of the two float bowl chambers.

    This spawned from another thread that was discussing differences in the design of the venturi bridge between the round tops and flat tops. At request from Blue, I made the measurements above.

    Quote Originally Posted by Blue View Post
    Could you do me a favour and post the volume/capacity of the flat top and round top carbs if you have a chance?
    I wasn't sure if it would have been better to post this in the original thread, but since it really had nothing to do with the content of that original thread, I thought it would be better posted in a new thread. Here's the original thread where the request came up:

    http://www.classiczcars.com/forums/s...ments-welcome)

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    Registered User 5thhorsemann's Avatar
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    Fuel pump volume and float valve size are much more significant than bowl volume. Larger bowl volume is a bad thing if your car is a weekend worrior, the blended gas varnishes in the bowl, if there is more of it, it leaves more varnish.

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    Oh, okay....

    Sign me quizzical
    Bruce Palmer
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    Nova Scotia,Canada,Earth Blue's Avatar
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    Thanks a million Bruce.

    I'll measure the volume displaced by a round-top float here in Canada and I can get the volume of the flat top floats when I get back to the USA thanks to the generosity of SteveJ providing a carb for the project.
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    No, no... Don't worry about the float volumes. Those measurements I took were with needle valves and floats installed and working as used in application. I was thinking about it and was giving myself a headache trying to decide if there was validity in measurements without floats and Archimedes appeared to me in a vision and made fun of me because I couldn't figure it out.

    So I just bit the bullet and did it with valves and floats installed. I didn't spend a lot of time getting the float levels spot on, but they're pretty close. (That's one of the "shortcuts" I allowed myself to take.)

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    Default Round Tops vs Flat Tops Float Bowl Volume Capacity

    If you have a spring loaded float needle plunger, float height is set just resting and without compressing the plunger.

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