Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Did they mix the parts ?

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Erick:
I'm new to this forum and of course I'm having problems with my carburetor.
I recently changed my Corvette carburator from Holley to a Quadrajet.
So I'm the "lucky" owner from a uremco "remanufactured" Q-Jet.
Because I was unable to adjust that carb, I made some research and with the help from the net, Lars from corvette forum and Cliff's book, I discovered what those "remanufaturers" are able to do. On my carb were missing power piston bottom pin, air horn main air bleed, main body main air bleed and  idle air bypass was plugged.
Before going further and order a recalibration kit for my aplication, I would like to be sure that they don't mix the parts, so i hope that with the following pictures one of you will be able to tell me if airhorn and base plate are the good ones for that 1972 350CI truck carb (704 2210 ).

Kenth:
Looks like a genuine 7042210.
These units have .120" MAB´s in airhorn and float bowl, no brass inserts.
Cut power piston is a bummer, never understood why they do this.
Plugged idle bypass air is a cheap way to richen up the low speed circuit, doesn´t work well with ported source to the ignition vacuum advance.
Factory jetting is 43B primary rods, #74 main jets and DA secondary rods.

Erick:
Thank's Kenth. Finally some good news. It seems it will possible to adjust that carb.
I machined a new pin for the power piston which I re-sleeved in place and removed the lead plugs.
So now engine idle is much better, sparkplugs are no more black and the idle mixture screw finally useful.
But there are small hesitations at cruise around 2000RPM, slight engine stumble.
Factory jetting is ok ( 43B primary rods, #74 main jets and DA secondary rods)
Idle tube and idle down have also been changed by remanufacturer, I don't know if it's orginal manufaturer size for that carb
idle tube : 0.029
idle down restriction : 0.047
So I suppose there are some modifications to do with my engine specifications.

Kenth:
As for the idle circuit i have found the 1972 Chevy Truck Qjets have .039"-.040" idle tubes, .092" upper idle air bleeds,  .051"-.052" idle down channels, .063" lower idle air bleeds, .095" idle bypass air holes in throttle plate and .086" idle needle holes.

HTH

Erick:
So upper idle air bleeds, lower idle bleeds and idle needle holes, jets and needles are the good size
Idle bypass holes are larger .0137
idle tubes smaller  0.029
idle down chanel restriction smaller  0.047
I don't know the possible effects from those changements.
Kenth, thanks for all those informations.

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