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Old 04-24-2005, 11:36 AM
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Holley power valves

Here is a theory question:
What kind of problems would a power valve opening at idle cause? I understand 100% how to spec the proper size p/v, I'm just wondering how much effect it will have on the idle circuit and what problems one could expect. From what I can determine from reading my holley books, the idle circuit draws fuel from the main well. The main well gets fuel through the main jets and if the power valve is open it to would be adding more fuel to the main well. So in theory, one could expect idel mixture to be overly rich.
Anyone care to comment or provide real life experience.

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Old 04-24-2005, 12:02 PM
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power valve

When idling the butterfly valves are closed and the vacuum is acting under them. So at idle there is not enough vacuum in the main body to siphon gas up from the well into the boosters. (If there is, your secondary butterfly valves are not adjusted correctly. A tell tale sign is not being able to get the engine to idle down.)

The idle circuit consists of slots at the bottom of the carb. As you accelerate slowly the butterfly valves open exposing more of the slot allowing more fuel to enter with the extra air. Once the butterfly valves open pass the idle slots the vacuum increases in the main body enough to pull fuel out of the well. (This is where you will notice a bad power valve. You will burn rich up to about 1/2 throttle.)

The power valve can be removed if you increase jets 3 to 4 sizes.

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Last edited by bracketeer; 04-24-2005 at 01:14 PM.
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