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Adjusting Carb after rebuild...

Discussion in 'The Garage' started by socal chevy, Apr 7, 2005.

  1. socal chevy

    socal chevy 1/2 ton status

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    What do I need to adjust when I reinstall my carb after I rebuilt it? EXPLAIN> :)
     
  2. 1-ton

    1-ton 1/2 ton status Premium Member

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    It depends on what type of carburetor you have. I am going to assume it is a Rockchester Quadrajet.

    1. First, you need to adjust the idle mixture screws. To set them in the ballpark for initial start up, screw them in until they are seated, then screw them both back out two turns.

    2. The next thing that needs to be adjusted is the choke. To do this turn the choke cover counter clockwise (while the carburetor is cold) until the primary throttle choke plate has about a 1/16" gap between the choke plate and the primary throttle horn.

    This should be enough to get the engine started. You will have to adjust the idle (on the carb linkage) after the engine is started.
     
  3. socal chevy

    socal chevy 1/2 ton status

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    Thanks for the info, but I need pictures of something. I dont know which screw is which, or where it is. :confused: :D
     
  4. akbound

    akbound 1/2 ton status

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    Go to Autozone or whatever you have and get a Haynes Techbook Rochester Carburetor Manual. Plenty of pictures and step-by-step instructions. IIRC it was ~$12.
     
  5. socal chevy

    socal chevy 1/2 ton status

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  6. mosesburb

    mosesburb For Rent Premium Member GMOTM Winner

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    If you need pictures etc, you NEED to get a manual. I am not familiar with the one previously mentioned, but I bet it will help you immensely. I have a book by Doug Roe on Rochester Carburetors published by HP Books, that is a great wealth of odd information pertaining to these carbs (I actually had to dig it out a few weeks back when I got a vehicle in with a bastard two-year only Q-jet on it). Either one will help you solve your issues and have info on what to look for while tuning etc. I got mine at one of the typical bookstores in the area, but I know some parts stores sell them as well.
     
  7. BIG STEVE

    BIG STEVE Registered Member

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    The ajustments you make while rebuilding it are very critical float leval
    metering rods be shure and have the exact specs with the idle screws
    use a tach 2 out is a good starting place then move in or out to find the highest idle then set to idle spec with linkage set screw.
    The secret to chokes are to set it to open back up asap
    Chokes cause more eng wear than about any thing oyher than non maintanace Years ago a gm rep told me the biggest reason for the vast
    increase in engine life was when the went to automatic chokes.
    Good luck

    90 jimmy gotta love fuel injection
    02 gmc HD
     

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