Auto or manual, whats different?

Discussion in 'The Venerable Q-Jet' started by chrome yellow, Aug 15, 2006.

  1. chrome yellow

    chrome yellow Well-Known Member

    What is the difference between a quadrajet for an automatic as opposed to a stick shift car? I have a 7043245 on my 72 350. I used the search function but did`nt see an answer to this question. Thanks, Brad. :TU:
     
  2. copperheadgs1

    copperheadgs1 copperheadgs1

    I believe the only difference was the jetting as a 4-spd was jetted richer. Not an issue as is easy to change to what you want anyway.
     
  3. carbking

    carbking carburetion specialist

    As a general rule (remember, general rules are meant to be broken :laugh: ); the major difference between a manual transmission carb and an automatic transmission carb is that the carb designed for the automatic will have a richer overall calibration. This is necessary to compensate for the fluid losses in the automatic transmission.

    Since the calibration will consist of metering of the fuel (jets and metering rods), and metering of the air (air bleeds, restrictors, etc.); this calibration is not always obvious if one looks only at the rods and jets.

    There may be other differences in vacuum ports.

    As another general rule, for interchange purposes:

    (A) a carb designed for an automatic may be used on a manual car with a slight loss of fuel economy.

    (B) a carb designed for a manual car MAY have lean issues if placed on a car with an automatic; and probably should not be used without modification to the carb.

    Jon.
     
  4. copperheadgs1

    copperheadgs1 copperheadgs1

    Well at least in 71 the 350 4 spd carb is jetted richer with 69 jets and 44 rods. The auto carb has 68 jets and 44 rods.
     
  5. jamyers

    jamyers 2 gallons of fun

    From what little I've seen looking in Buick chassis manuals, most often everything but the jets and rods were the same, with one or the other jetted richer. Easy to change.
     
  6. chrome yellow

    chrome yellow Well-Known Member

    Thanks for the info everyone. I do still have the carb that was original to the engine and I may just rebuild that one. Brad.
     
  7. bignastyGS

    bignastyGS Maggot pilot

    You are kidding....Right??? Thats the elusive carb that has been haunting me..

    Been after one of them a long time for my 73 GS 350 4 speed...lol
     
  8. chrome yellow

    chrome yellow Well-Known Member


    Sent you a p m. Brad.
     

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