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Stupid carby

Discussion in 'The Hokey Ass Message Board' started by Jasper6120, Mar 18, 2009.

  1. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    Hello I have a stromberg 2 barrel carby which has been running like crap and making me very depressed. Basically what is happening is the engine seems to be running really smooth, strangely smooth, not lumpy at all and when I sit at idle the carby works for a while, but gets slower, slower and eventually dies. When it dies it drips fuel onto the manifold. What should I do to fix the problem? Anything short of putting the garden hose on it and using it as a sprinkler would be great. Cheers
     
  2. This is , of course , an obvious problem . In Australia the carb is upside down and all the fuel drains out . If it were in the US I might suspect you have float problems
     
  3. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    But of course.. I fixed this problem by putting wheels on the roof. I've maneuvered the float a few different ways but always ends up with the same result. The needle and seat seem to be sealing perfectly fine and float is currently sitting at the specified height. Curious.
     
  4. Check the fuel pressure.
     
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  5. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    Pressure is tops, I put a new fuel pump on recently.
     
  6. cornfieldrodder
    Joined: Sep 20, 2002
    Posts: 967

    cornfieldrodder
    Member

    Fuel drips from where?
     
  7. parksquijada
    Joined: Aug 6, 2008
    Posts: 316

    parksquijada
    Member
    from norcal

    float not floating..?
     
    Last edited: Mar 22, 2009
  8. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    It seems as though it is dripping out of the lower butterfly spindle on the left side of the car (Drivers side USA). The float floats fine. I can usually sort out a problem with a carby in no time but this has got me perplexed.
     
  9. The pressure should be no higher than 3 PSI per carb. Also what kind of car? Is the tank higher than the carb? I have had this problem before. Turned out that in my model A with stock tank, under a full tank situation the weight of the gas pushed the gas past the needle/seat.
     
  10. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    Verdict was a blocked idle circuit. As for the leaking? Needle wasn't sealing 100 percent and it was a leaky carb anyway. I have another question. Are all standard 750 cfm rochester quadrajets jetted much the same regardless of the engine they were originally pulled from? Does anyone know?
     
  11. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,008

    FiddyFour
    Member


    no, there is nothing standard about a q-jet. depends on the make and model of the donor car. q-jets are amazing animals if they're tuned in the hands of someone who knows them well... but they are a royal piece of shit otherwise.
     
  12. carbking
    Joined: Dec 20, 2008
    Posts: 2,613

    carbking
    Member

    The Rochester Q-Jet (my opinion) is the second finest street 4-barrel ever built.

    That being said, Rochester built HUNDREDS of different versions, as the Q-Jet is versatile enough to use on many types of applications.

    If migrating an original equipment carburetor from one application to another (any original equipment carburetor), for best results remember:

    (A) Displacement of the two engines should not vary more than plus/minus 3 percent.
    (B) Type of engine (oversquare, undersquare) should be the same.
    (C) A carb designed for a manual transmission should not be used on a vehicle with auto transmission.

    Violation of any of the above 3 "rules of thumb" will result in either carburetor modifications being necessary, or less than optimal performance.

    These rules of thumb do not necessarily apply to aftermarket carbs which generally have a much lower (richer) A/F ratio.

    Jon.
     
  13. parksquijada
    Joined: Aug 6, 2008
    Posts: 316

    parksquijada
    Member
    from norcal

     
    Last edited: Mar 22, 2009
  14. Southfork
    Joined: Dec 15, 2001
    Posts: 1,463

    Southfork
    Member

    I don't suppose that Quadrajet carbs are marked in some way to indicate the make and model of the factory donor car? It would seem that using a used Quadrajet could a big crap shoot unless you are a experienced/trained carb technician. Really?
     
  15. oj
    Joined: Jul 27, 2008
    Posts: 6,200

    oj
    Member

    Hey Jasper, the only thing that will let the engine idle down until it shuts off is a vacuum leak. That is for sure, sun rises in the east kind of thing. If there is dirt in idle ckt then it wouldn't run at all, if it idles then slows down until it just shuts off it is sucking air from somewhere else than thru the venturii.
     
  16. rails32
    Joined: Oct 29, 2008
    Posts: 110

    rails32
    Member

    q-jets came in 2 sizes from GM 75o cfm for small blocks and 850 for big blocks. There is a number stamped into the driver side of the carb on the secondary side as an example=1753241.The first two numbers tell what division of GM the carb is from. Use this number at a parts house to get a rebuild kit. Always get a new brass float ,todays gas can eat into the plastic ones. Doug Roe had a book out on them that is still available. I use to run them in S/S classes and on the street.When set up properly they run great and get good fuel econmy. The biggest problem with old ones is leaking plugs on the bottom of the fuel bowl. The common fix for years has been to put fuel proof epoxy on the plugs when rebuilding them.
     
  17. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,008

    FiddyFour
    Member

    do yourself a favor if you're planning on messing with q-jetsm... get the book rebuilding and modifying the rochester quadrajet by Cliff Ruggles...

    great book, well written and lots of information and pics... for the money, it cant be beat in my opinion
     

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