Thread: Power Valve
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Old 11-07-2004, 10:14 PM
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Re: Power Valve

Whats the carb number? It should be 4 digits on the choke horn, on the top of the carb.
Power valves only vary on the amount of intake manifold vacuum needed to close the valve.
My Holly book shows 2 different valves for your carb; Holly part # 25BP-591A-85 or 25BP-591A-65.

The first one will open (add fuel) with a relatively less throttle opening than the second one.

BTW a 780 carb is a little big for a 350. A 650 might sharpen thrings out a bit.

If its not the power valve, try leaning out the primary jets about 2 points. EVERY aftermarket 4bbl Holley carb is jetted TOO RICH from the factory. Every one, no kidding!! It's as if they expect every carb they build will go right one a 454 with a 6-71 blower.

You should have a #69, 70 or 71 jet in there, so try #67, 68 or 69 jet.
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