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Discussion Starter · #1 ·
i put a 4MV quadrajet on a small inline 6 (holden 202)
it drives ok and is even ok at full throttle
it just won't idle i even drilled the Idle Channel Restrictions

it seems like the idle circuit is blocked :banghead3
 

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It has been a long time since I've rebuilt one. I've always checked out circuits by spraying penetrating oil or carb cleaner through each one. Air doesn't tell the whole story. I do remember having idle circuit problems. Seems like they easily plug up. If you have put new gaskets in it make sure the gasket isn't plugging up any of the circuit holes. If you haven't maybe the previous owner put the wrong one in it. There are many different applications.

They are a great carb for gas mileage if you don't open the secondaries.
 

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Discussion Starter · #3 ·
it didn't seem blocked when i spayed carb cleaner through the idle and main circuits
but it behaves like there is no ideal circuits
it will idle really roughly at 1300rpm but its like its idling on the small amount of fuel its starting to pull from the boosters
im new to quadrajets i usually run holleys
 

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well dispite what people say a q-jet is a easy carb, I would say a good rebuild is in order, let all the parts soak 24 hours. Its probably just some trash cought up in it
 

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There should be a stop screw on the secondaries. It should be adjusted just enough to keep them from wanting to stick in the closed position. Also, compare the venturi cluster gaskets to the cluster and carb. body to make sure the possibly incorrect gaskets are not blocking any passages. Don't rule out the possibility that there is an air leak somewhere else in the induction system. When they were popular, I rebuilt many Q-Jet carbs. and never had an idle circuit problem. Sinking floats and leaky wells yes, but never an idle circuit.
 

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Discussion Starter · #9 ·
i had a 350 holley on the engine (adapter plate to the 4 barrel manifold)and had no problems only the carb has changed
i suppose there is a slight chance the holley could be adjusted rich enough to mask a small air leak

the Q-jet is off a 308ci V8 so would have been calibrated for that
but the idle circuit wasn't the area that i though would be a problem
i just thought some adjustment on the mixture screws and idle would be fine
 

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Discussion Starter · #10 ·
Missing idle bleed restrictors:
Results in: Poor idle, ineffective idle mixture screws, off-idle hesitations, very high idle required to keep engine
from dying when placed in “drive,” fuel discharging out main discharge nozzles at idle.
Comments: Different Q-Jets have different idle bleed calibrations. Part of this calibration is the installation of some
brass restrictor orifices in the venturi area/booster ring area. Many commercial rebuilders will actually remove the
orifices during rebuild, causing too much air to be pulled into the idle fuel circuit. The engine will then only idle if
the idle speed is run up into the transition & cruise metering circuit. This is a difficult problem to diagnose and
correct, since some Q-Jets did not use the restrictors, and replacement restrictors are not serviced separately.
this may be it
 
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