All youll need is a screwdriver and a good vacuum gauge. Here we show you how to properly adjust the curb idle speed on your holley carb.
Carburetor Set Up And Lean Best Idle Adjustment
Holley carb fast idle adjustment. Turn the engine on and allow it to idle. First find your idle rpm setting from under your hood or from a repair manual. Step 6 adjust all of the idle mixture screws by turning them clockwise and counter clockwise until the vacuum gauge reads the highest possible vacuum reading. Reduce the idle speed and repeat the process perhaps several times until the engine idles at the desired engine speed. Make very slight adjustments here as the factory setting is very close to ideal. This quick walk through will get your holley carb up and running with a perfect idle in no time.
On a manual transmission car the idle speed adjustment can be set with the transmission shifted into neutral and the parking brake is set. Continue to turn each screw in 90 degree increments while listening to the engines idle speed. This is the idle stop adjustment for most holley carburetors. At that point you can go ahead and snug those screws back up and thats going to give you a good starting point to make adjustments from. Holley carburetors feature idle mixture screws which control the airfuel ratio and these are usually the main culprits in an improperly idling carb. Slightly crack the throttle open unload the fast idle cam and turn the choke cap clockwise until you see the choke plate open.
Once the engines idle speed has begun to slow back each idle mixture screw out 90 degrees to complete the process. To access the carb must be inverted. Turning the screw clockwise will. Turn each idle mixture screw one at a time in a clockwise direction 90 degrees. Then rotate it back slowly until the choke plate just comes closed. Recheck the front idle after the rear setting has been confirmed.
If your aftermarket holley is equipped with four corner idle circuits such as the 4781 shown in the photo set the front first then set the rear.
Gallery of Holley Carb Fast Idle Adjustment
