Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Venturi's in action in idle

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Marx3:
Inferior kits are no doubt about it, not worth the effort installing! But now I know your site, right :)

btw, would you explain the physics of the venturies flowing fuel, I cant get it into my head.  Is it the lack of available air from the bypass system that creates a stronger signal in the boosters?

77cruiser:
With too much airflow through the venturis they're going to pull fuel. Does the carb have an idle bypass?
Can you increase your timing to bring the idle up & then close the throttle a bit?

Marx3:
Obviously is airflow sucking the fuel out of the venturi's :) But why!!! Is it solely because of some fault in the idlebypass system, or can it also be due to a wrong gasket?

I dont see the typical bypass system on the backside of the carb. Just the unused area and two unthreaded holes where the screws would be. Man I am confused on this one.

Marx3:
Forgot to mention that on a Nailhead 425 idling at 600 rpm, 16-17 Hg, and about 35 degrees of advance ( with manifold vacuum ) they still distributed fuel... really weird.

Cliff Ruggles:
Did you pull the idle tubes during the rebuild to make sure they were not blocked or obstructed?  In most cases they will have considerable debri, dirt, corrosion in and under them. 

When placed in service with insufficient idle fuel, the idle speed screw will need to be turned in to sustain the engine, it pulls fuel from the boosters (nozzle drip).....Cliff

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