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Category: Categories > Engines > Engine Tuning > Tech Tip

	Author's Name: HOWEMOTORSPORTS	View author's other Tech Tips
	Author's Username: HOWEMOTORSPORTS	Ask the Author a Question or View Answers
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Here is something I get alot of requests about. Assuming you have tried different squirters and can not get that stumble to go away,here is a neat cheap trick to fix those double pumper holleys 4150 and 4500 series. I have had countless racers at the track come to me with this same problem they have jetted and changed squirters and the car still has a stumble. This is one thing to do. Hold the carb in the wide open position and take a flat screwdriver and bottom out the pump lever on the pump you need about .015 between the pump and the pump arm with the carb at WOT, adjust the arm to .015 and try it again, if you still have a stumble the spring in the arm may need shimmed this can be done by taking the spring bolt and nut apart and using the teflon bowl washers they sell at most auto parts stores for float bowl washers and use them to tighten the spring up, just stack them above the spring between the arm and the spring. One way of checking is to do this, with fuel in the bowls open the carb quickly and watch to see if you have a space apear between the pump arm and the adjuster nut while opening the throttle on the carb, you want clearance of .015 and no space between the nut and the arm. This should cure the stumble in your holley. NOTE***** This is for gas applications.