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tuning a holley?

Discussion in 'The Garage' started by Cornfield creations, Apr 9, 2007.

  1. Cornfield creations

    Cornfield creations 1/2 ton status

    Oct 19, 2005
    Likes Received:
    Jasper, Indiana
    I got a holley 1850-S. I am mainly trying to learn how to fine tune it. It was tuned previously, but we had to have it taken apart off the car, and I feel the settings are off. So as far as idle mixture and any other settings, how do I go about it?
  2. rcamacho

    rcamacho 1/2 ton status

    Jul 1, 2004
    Likes Received:
    Pick up a good Holley book off ebay/Amazon, etc. This is one of my favorite basic books:
    Holley Carburetors (S-a Design) (Paperback)

  3. fried_guy

    fried_guy Registered Member

    Mar 7, 2007
    Likes Received:
    Fallbrook, CA
    The first thing you want to do is set your transition circuit. Turn the carb upside down and make sure the transfer slot is "square" (not rectangular) by raising or lowering your idle speed. Remember where this setting is (ex: 2.5 turns out or so).

    Then set your secondaries so that they are barely open... about 1/4 turn from fully closed... only so fuel doesn't pool on the secondary butterfiles.

    Then install the carb, prime the fuel bowls, start the engine and time it, set the float levels to just below the sight plugs and set the idle mixture with a vacuum gauge (my preferred method) or a tachometer. You may need to raise the idle speed to get it to idle properly as a temporary measure.

    Then adjust your squirter and pump cam to your desired performance level, get the correct size power valve(s), and then adjust the jets if necessary. All this is pretty much trial and error unless you can make a good estimate based on previous experience or have a/f ratio meters.

    Put the idle speed back down so that the transfer slot is square again (ex: 2.5 turns or so)

    If you need more RPMs, you can open your secondaries up a bit more, drill holes in the butterflies, adjust the timing etc. But don't raise the idle speed much as it will mess with the transfer circuit.

    After all that, adjust your idle mixture one more time, double check everything, set your choke, and you're pretty much done.

    Holly carb tuning in a nut shell.

    Here's a great website with some more info: http://www.bob2000.com/carb.htm

    If any of this is foreign to you get the book recommended above... it's a good read.

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