What should the idle speed be on a Holley carb?
What should the idle speed be on a Holley carb? Engine idles rough and stalls: Correct idle speed setting. Adjust idle mixture screws to lean best idle. Repeat the operation on 2 and 4V carburetors. Now, turn mixture screws in until idle speed drops 25 RPM on tachometer. Idle speed setting. Re-set idle speed per instructions on decal in engine compartment. Why does my Holley engine stall at idle? Holley carburetors have idle mixture screws that control the air/fuel ratio at idle. Improperly set idle mixture screws are often the reason for carburetor symptoms such as hesitation, rough idle, backfire,...