How To Set A Stoichiometric Idle On A Holley 0-3310 Carburetor

 Before You Begin

This procedure applies specifically to:

Holley 0-3310 Carburetors

Recommended tools:

• Flat blade screwdriver
• Notepad and pen
• AFR gauge (if equipped) 

If your vehicle is equipped with oxygen sensors or a wideband AFR gauge, use those readings to assist with fine tuning.

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Step 1: Warm Up The Engine

1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. Wait until the thermostat opens and coolant temperature stabilizes. 

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Step 2: Record Current Idle Mixture Settings

Before making adjustments:

1. Locate the idle mixture screw on both sides of the carburetor.
2. With the engine running, gently turn one mixture screw clockwise until it lightly seats.
3. Count the number of turns as you move the screw.
4. Return the screw to its original position.
5. Repeat for the opposite side.
6. Record the setting for both screws

Important

• Count adjustments in 1/8-turn increments.
• Do not force the screws against the seat.
• The engine may stall during this process. If it does, return the screw to its original position and restart the engine. 

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Step 3: Set Desired Idle Speed

Locate the idle speed screw.

Typical Idle Speed

For most BluePrint carbureted applications:

800-850 RPM

• Clockwise = Increase RPM
• Counterclockwise = Decrease RPM

Set and record your desired idle speed before moving on.

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Step 4: Determine Correct Idle Mixture Setting

Using the table below, identify the recommended number of turns from fully seated based on your idle speed and coolant temperature. 

Idle RPM	180°F Coolant	200°F Coolant
750	5/8 Turn	3/4 Turn
800	5/8 Turn	7/8 Turn
850	3/4 Turn	7/8 Turn
900	3/4 Turn	7/8 Turn
950	3/4 Turn	7/8 Turn
1000	7/8 Turn	1 Turn

Altitude Adjustment

The table was developed at approximately 2,200 feet elevation.

Adjust accordingly:

• Lower elevations: Slightly more turns
• Higher elevations: Slightly fewer turns 

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Step 5: Adjust Both Idle Mixture Screws

1. Turn the idle mixture screw clockwise until it lightly seats.
2. Turn it counterclockwise to the recommended setting from the table.
3. Repeat on the opposite side.
4. Both sides must be set to the same number of turns. 

Important

Make adjustments in 1/8-turn increments.

If the engine stalls:

• Finish the adjustment
• Restart the engine
• Verify settings again 

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Step 6: Fine Tune Using An AFR Gauge (If Equipped)

If you have a wideband oxygen sensor installed:

Target idle AFR:

14.3-14.7 AFR

Adjustment Direction:

• Clockwise = Leaner
• Counterclockwise = Richer

Make adjustments in:

1/8-turn increments

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Additional Notes

• Do not run the idle mixture screws less than 1/2 turn from fully seated.
• Final tuning should be completed with the air cleaner installed whenever possible. 
• Altitude, air cleaner design, temperature, and engine combination may require minor adjustment from the baseline values.