tuning holley carb

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Mar 14, 2007 | 10:22 PM

trucknut7

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Joined: Jan 2007

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tuning holley carb

i have a 79 ford f700 with an 8 cylinder engine and a holley 4 barrell carb. i recently rebuilt the carburetor and want to set the fuel mixture screws. i hooked up my vaccuum guage and tachometer and started at 1.5 turns out with the rpms at 850. the vaccuum does not seem to vary as i adjust the screws a 1/4 turn at a time. i left both screws at 1&1/4 turns out and it seems to run ok. any suggestions for fine tuning?

Mar 14, 2007 | 10:28 PM

LxMan1

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Joined: Dec 2001

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From: Louisville,Ky.

Turn them in until the vacuum starts to drop, then back them out until it tops out again and leave it there. It should be fine.

Mar 18, 2007 | 12:30 AM

kermmydog

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Joined: Oct 2003

Posts: 9,176

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From: Western Central NV

LxMan1 is right unless you have a reverse idle Holley. Then you adjust the opposite way. In the 70s Ford had reverse idle Holley carbs on some engines. Where the idle adjustment screws are in the metering plate, just above the screw it should be marked with an arrow pointing counterclockwise. If it is a Reverse Idle carb.