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setting air/fuel screws on Holley carb.

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Old 05-12-2002, 05:53 PM   #1
candyapplevette
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Default setting air/fuel screws on Holley carb.

What is the correct way to set and adjust the air/fuel screws on a Holley 750 double pumper with the 4 corner idle system?
I have been told by some local people to set all 4 screws the same and I have also been told to set the back ones approx. 1/8 to 1/4 turn out only.
What is the proper way to set this carburator? All of the Holley's I used to run were the old style with 2 air/fuel screws.

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Old 05-12-2002, 06:18 PM   #2
Larry B.
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Default Re: setting air/fuel screws on Holley carb. (candyapplevette)

Just adjust them for the smoothest idle or if you have a vacuum gage then obtain the highest vacuum reading. ;)
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Old 05-14-2002, 04:01 PM   #3
norvalwilhelm
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Default Re: setting air/fuel screws on Holley carb. (candyapplevette)

All the holleys I have delt with idle too rich. I usually have a healthy cam so it doesn't help. I always drill about .100 hole in each of the throttle plates. The placement is important. I then install a .015 wire in each of the idle circuit passageways. You are trying to establish 1 1/2 turns out from bottoming the idle screws. This is where they are ment to be. If they are almost closed to get a descent idle something is not right. The throttle plates should also be closed. Too open and the transferr slots start adding to the idle mixture. I the throttles are uncovering the transferr slots the idle screws will be insensitive.
I set front and back the same. Try for the best idle at around 1 1/2 turns.
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Old 05-14-2002, 07:42 PM   #4
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Default Re: setting air/fuel screws on Holley carb. (norvalwilhelm)

First I turn all screws 1 1/2 turns out then get the vacuum gauge and since I only have two hands I set the primary first then the secondary :D


[Modified by MotorHead, 5:43 PM 5/14/2002]
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Old 05-14-2002, 08:31 PM   #5
clem zahrobsky
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Default Re: setting air/fuel screws on Holley carb. (candyapplevette)

take the carb off the engine,set the idle speed screw so only .040 of the idle transfer slot is showing. set the butterflys on the secondary side to be open the same amount. install the secondary stop screw in upside down so you can turn it from the top. put the carb back on and if it does not idle fast enought take it of and drill all 4 butterflys with a 3/32" drill about 5/16" of a inch from the edge,centered towards the outside edge of the butterflys. all DP are very rich on idle and you can put the wire into the IFR or solder them up and redrill them smaller :chevy
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