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Thread: A Carb builders worst nightmare

  1. #11
    Hotcrusader76
    To some extent I don't think it's Holley. It's the people who sell or represent them. But then again I have seen many new Holley's out of the box internally and it makes me question there Qaulity assurance dept.
    At any rate...Buyer beware..
    ~Ty

  2. #12
    Froggystyle
    Hotcrusader76:
    At any rate...Buyer beware..
    ~Ty That is just good advice, whether it is carbs or apples.
    The problem with carbs to me, is that they are really the last unknown thing on any boat I build. I feel 100% confident with anything related to fiberglass, interior, fuel delivery to the carb, mechanical, valvetrain, trailer, etc... But I look at that ugly thing on top of the motor and just want to shake sticks at it and sacrifice chickens. I have never understood how it really works, and for some reason don't want to learn. If it works, I am not pleased... I am amazed. When I "tune" a carb and it runs better, I figure I have a new lucky pair of underwear on or something. BTW, "tuning" for me is essentially idle screw and idle mixture. Past that... Completely lost.
    When they come from the factory broken... I have a problem. I don't want to become a carb expert. I want to bolt on something that properly regulates fuel according to demand on a given rpm curve. It should be simple... 509 cubic inches, 3000 rpm... you should know how much fuel and air you need.
    But it isn't. So, until the day when injection becomes bolt on without a degree from MIT... I am very pleased I know a carb guy!

  3. #13
    cyclone
    3 words..Holley HP Series...i've run about 10 of those carbs on various motors and other than jetting changes, they've needed nothing. All of them worked great right out of the box. I"ve had great luck with the race-series Demon carbs too.

  4. #14
    78Eliminator
    I just think it's funny how this thread is called "A Carb builders worst nightmare", then it goes into the fact that a lot of carbs are not so great out of the box and "Buyer beware".

  5. #15
    Infomaniac
    Froggystyle:
    Hotcrusader76:
    At any rate...Buyer beware..
    ~Ty That is just good advice, whether it is carbs or apples.
    The problem with carbs to me, is that they are really the last unknown thing on any boat I build. I feel 100% confident with anything related to fiberglass, interior, fuel delivery to the carb, mechanical, valvetrain, trailer, etc... But I look at that ugly thing on top of the motor and just want to shake sticks at it and sacrifice chickens. I have never understood how it really works, and for some reason don't want to learn. Too late pay attention:
    Carbs work due to differential air pressures.
    The float chamber vent directs atmospheric air pressure to the fuel in the float bowl. This is the high pressure.
    The venturis inside the throat of the carb cause the air to accelerate when it flows through. This causes a low pressure. The fuel discharge is located here.
    The difference in the high pressure air (atmospheric) in the float chamber and the low pressure air in the venturi cause fuel to start flowing.
    The greater the difference in these 2 pressures the more fuel flows. Fuel is metered through the jets on the way out.
    More air flow is caused by throttle opening. open the throttle, more air flows through the venturis causing a greater pressure drop which causes more fuel to be drawn out of the float chamber. Or pushed out however you view it.
    The level of fuel in the float chamber must be kept just below the discharge level so gravity does not flow fuel for you. The difference in air pressures must lift the fuel through the passages enough to discharge it. The fuel level in the float chamber can be adjusted up or down to affect how and when fuel flows.
    Easy enough? Other systems involved - acceleration system - power enrichment system - idle system - air bleeds.
    the idle system is pretty cool. Not enough air flow through the venturis to cause fuel flow so the idle system discharges under the throttle blades where there is a very low pressure. Manifold pressure. A lot lower than what is created in the venturi. To keep fuel from running out there all the time the fuel is lifted much higher than the main discharge nozzles before it can get down to the idle discharge.

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