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Holley Tuning Part 2

To set the choke blade angle, bend the small wire link between the choke pull-off and the choke fast idle cam cage as seen in picture #2 below. Shortening the link will cause the choke pull-off to pull the choke blade open farther for a leaner idle mixture, and lengthening the link will open it less for a richer idle mixture.

Holley Carburetor choke blade angle

To adjust the curb idle speed, the engine will need to be at full operating temperature and the choke will need to be completely open and dis-engaged. To verify this, make sure the fast idle lever is not resting on any of the steps on the plastic fast idle cam.

Holley Carburetor curb idle speed

To raise the curb idle speed, turn the screw clockwise as shown in Pic. 3 above. To lower the curb idle speed, turn the screw counter-clockwise.

To adjust the idle mixture trim screws, the engine will need to be at full operating temperature and at curb idle speed. Begin by slowly turning the mixture screw (as shown in picture #4 on the following page) in (clockwise) no more than 1/8 of a turn at a time until the engine stumbles, then backing out again just until the stumble clears up. Then turn the screw back out an additional 1/8 turn. Repeat this process on both mixture screws (one on each side of the carburetor).

If you experience difficulty in getting the trim screws adjusted, turn the engine off completely and re-establish a baseline setting by gently turning the mixture screws in (clockwise) until you feel them lightly bottom out.


Then turn each screw out (counter-clockwise) 1 & ¼ turns. This is your baseline setting. Repeat the process until a stable, smooth idle is obtained.