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Thread: Cat Ten Carb

  1. #11
    Join Date
    Jul 2014
    Posts
    238

    Default Ten carb

    Ten carbs are out there but expensive, I have seen John Deere H carbs used a direct fit and runs good

  2. #12
    Join Date
    Apr 2007
    Location
    Elkhorn, WI
    Posts
    3,788

    Default

    Quote Originally Posted by JaxCatTen View Post
    Thank you all for the ideas and encouragement. I'm leaning towards the Ford 8N carb right now, it looks easy enough to make an adapter for and the price is right at just over a Benjamin. Using the formula to calculate CFM for the carb, with 143 ci @ 1500 rpm I should need about 50 CFM. I'll do some research to find the engine specs for the ford and compare.
    Thanks again.
    Jack
    This Carb is similar in flow to the Model A carb, so it would work!

  3. #13
    Join Date
    Nov 2018
    Location
    Cape Cod Mass
    Posts
    7

    Default

    Based on those numbers for the 8N, it would be 58cfm I need about 50cfm, looks good enough for government work... The biggest variable in calculating the cfm, is the efficiency of each of the engines, I used a generous 75%, for what I'm trying to accomplish, I think this will be just fine.
    Again, thanks to all that responded.

  4. #14
    Join Date
    Apr 2007
    Location
    Elkhorn, WI
    Posts
    3,788

    Default Calculating CFM

    I never got that deep into Carb's, how hard is it to calculate CFM?
    What steps need to be done to do it?

  5. #15
    Join Date
    Nov 2018
    Location
    Cape Cod Mass
    Posts
    7

    Default

    The formula for calculating how much CFM (cubic feet per minute) an engine requires is: CFM = Cubic Inches x RPM x Volumetric Efficiency 3456.

    The volumetric efficiency is the most difficult piece of the puzzle. Any ordinary stock automotive engine will have a volumetric efficiency of about 80%, Im using 75% for my calculations.

    Example: Using a 143 CID engine x 1,500 max rpm = 214,500

    Take 214,500 x .75 = 160,875

    Then 160,875 3456 = 46.55 CFM

    Add in a fudge factor of 10% and you get 51.2 CFM, anywhere around 50 CFM would work.

  6. #16
    Join Date
    Apr 2007
    Location
    Elkhorn, WI
    Posts
    3,788

    Default

    Thank You!
    So by taking 2 similar sized engines, a "swap" could be accomplished.
    I assume Carb suppliers must publish CFM somewhere for their products?
    Like way back when HOLLEY sold 600cfm and 800cfm 4 barrels?
    I know too many questions.....

  7. #17
    Join Date
    Nov 2018
    Location
    Cape Cod Mass
    Posts
    7

    Default

    You are correct, by using a carb from engines with similar CFM requirements, then they would be interchangeable. It would be easier if the MFG actually noted the cfm of the carb, but they don't normally do so. Even in the aftermarket, they don't always tell you what the cfm is. But yes some carb mfg's like Holley, did list their product by cfm size because they sold many different sizes, and it was up to the installer to pick the correct one. It is important to get close to the proper size so that it will function properly. To small and the engine won't be able to reach its full rpm (power) as there isn't enough air flow through the carb. To large and the throttle response can be erratic especially at just off idle / partial throttle operation. Then the top end will usually full off as well and run lean. I have seen a lot of guys install to large a carb on their street cars then wonder why it doesn't run and drive well, there is such a thing as bigger isn't better.

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