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Holley Power Valve

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Holley Power Valve
Holley Power Valve

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Reviews (3)

Q & A (1)

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Save BIG during Happy HolleyDays! For a limited time receive up to 20% off select Holley, Demon, Earls, Flowtech, Hooker, Mallory, Mr. Gasket, MSD, NOS, Quick Time, and Weiand products. Sale prices valid thru 12/31/16.

Standard flow. Available sizes include: 2.5, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5 and 10.5 in hg.

High flow (big window valve) for alcohol. Available sizes include: 2.5, 3.5, 4.5, 5.5, 6.5, 8.5, 10.5 in hg.


Tech Tip: 

Engine vacuum will hold the valve closed until vacuum drops below the cracking point, measured in inches of mercury (in hg) at which time, the valve will open and enrich the fuel mix.

It is quite common to put very low numbers in multi carb systems. The reason is that if standard single carb valves are used, it will cause the engine to be overly rich. When you are at a part throttle cruise at 55 mph (say, with a 12 in hg of manifold vacuum) and you squeeze into the throttle to go up a hill or pass a car, the manifold vacuum drops (say, down to 7 in hg) and all three power valves open. Normally, this will make the engine soggy & rich, since it has three times the fuel enrichment that it needs.

People will put in the lower power valves to delay the enrichment until nearly Wide Open Throttle. At WOT, the engine can normally consume the additional fuel without puffing black smoke or fouling plugs. The problem with putting -45 power valves in, is that it defeats the purpose of a power enrichment system. The enrichment system is designed to provide a slight increase in fuel flow as power requirements increase. If you install -45 power valves and they do not open until WOT, you lose the benefit of adding just a little bit of fuel when you squeeze the throttle a little.

A better way is to put power valve plugs (or very low numbers) in the front and rear carbs and use a standard power valve in the center carb. The best way is to put restrictors (PVCR or power valve channel restriction, which are small lengths of stainless steel piano wire) in all three carbs, which limits the amount of fuel that is added, not when it is added.

Customer Reviews

Rated 5 out of 5 by 3 reviewers.
3 reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Star

Verified Purchaser
Raleigh, NC

Great products from Holley

October 20, 2015
As usual you can trust Holley parts to work properly. ALWAYS use the new gasket supplied with a power valve change.
Yes, I recommend this product.
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Verified Purchaser
Lee's Summit MO

In stock and delivered fast

November 02, 2014
Its getting hard to buy items like this locally. Speedway has them in stock and their great service gets me what I need FAST!!!
Yes, I recommend this product.
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Lawton, OK


February 08, 2010
Restoring 1949 Ford F1 Pickup
Yes, I recommend this product.
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Product Q&A

1 questions : 1 answers

1 answers

Are these ethanol proof. Thanks Dane

Warr Acres, OK
July 02, 2015

Are these ethanol proof. Thanks Dane


July 02, 2015
Sorry Holley does not make a statement either way as to the compatibility of the power valve with ethanol. You may want to talk with Holley directly.
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