How do idle air bleeds work?
The air bleeds draw air into the idle fuel wells and into the main fuel wells where it emulsifies (mixes) before being discharged through the idle ports and transfer slots in the base plate as well as the boost venturii up in the carburettor’s main body. That’s where the carburetor comes into play.
What do idle feed restrictors do?
This idle feed restrictor is essentially the main jet for the idle circuit. The idle air bleeds in the carburetor also affect the fuel flow, but the component that has the greatest effect on idle fuel flow is the idle feed restrictor.
When should you change high speed air bleeds?
In addition, the high speed bleeds can affect how linear the fuel curve is — if the AF mixture tends to get richer with higher RPM (common with Holleys) then you need to go larger with the bleed. If the mixture gets leaner with higher RPM (uncommon) then go smaller with the air bleed.
What causes a carburetor to backfire at idle?
This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. Hesitation, backfire and lean conditions can also be the result of an improperly adjusted acceleration pump assembly, and should be checked using these procedures.
Why does my Holley 4 barrel carburetor stumble?
If your car or truck is equipped with a Holley four barrel carburetor and stumbles upon acceleration, more than likely the carburetor needs an adjustment to the accelerator pump assembly. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle.
How do you change the fuel nozzle on a Holley?
Start by increasing the fuel nozzle size up by three sizes. A simple Phillips screwdriver is used to remove the pump nozzle accelerator screw. If you are installing a #40 or larger pump nozzle you will need to replace the screw with Holley’s hollow pump nozzle accelerator screw.