How To Adjust Holley Carburetor

Knowing how to adjust a Holley Carburetor is a handy skill to have if you are into racing or high performance engines. There are many specialized  ways to  adjust a Holley Carburetor. The most common adjustment is the choke adjustment. All new Holley Carburetors come from the factory wet flowed and calibrated. "Out-of-the-box" factory settings on any new Holley Carburetor should be very close and require little adjustment. These Holley Carburetor choke adjustments are to aid you with fine tuning.

To adjust a Holley Carburetor,  you will need:

  • 1/4" open end wrench
  • Standard mechanic tools are needed when adjusting a Holley Carburetor

Note:  Before you begin the choke adjustment on the Holley Carburetor make sure the vacuum port is plugged.

  1. Locate the black choke cap on the driver side of the carburetor. Choke operation can be controlled by rotating the choke cap.
  2. Determine if your choke is "coming off too soon" or "coming off too late".  A choke that "comes off too soon" may cause engine stalling, surging, backfiring, stumbling, and/or poor drivability when the vehicle engine is cold. A choke that "comes off too late" may cause black smoke from the tail pipe, a rough idle, missing, poor gas mileage, and/or poor drivability when cold.
  3. If the choke "comes off too soon" using your fingers,  rotate the choke cap counter-clockwise ONE notch at a time until the choke operation is satisfactory. The choke setting from the factory is at the index position (center).
  4. If the choke "comes off too late" using your fingers,  rotate the choke cap clockwise ONE notch at a time until the choke operation is satisfactory. After making the final adjustments, start your engine.
  5. Visually inspect to make sure the choke plate opens completely.
  6. If the fast idle RPM is too high or too low SHUT DOWN YOUR ENGINE IMMEDIATELY.
  7. Locate the fast idle screw below the choke housing. (Advancing the throttle to wide-open will expose the screw.)
  8. Use the 1/4" open end wrench to turn the screw. (Turning the fast idle screw Clockwise will increase RPM and  turning the screw Counter-clockwise will decrease the RPM). Standard factory setting should give you an idle of 1500-1600 RPM fast idle speed.

Holley Carburetor has a technical service department that will answer questions for free. The Service department is open Monday through Friday 7am to 5pm CST.  TAlso, Holley Carburetor offers free tech support pages that can be downloaded and printed from their web site. These tech pages are part specific and offer really good diagrams which help in locating the specific parts that are needed while  adjusting a Holley Carburetor.

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