Power valve selection

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Apr 3, 2004 | 08:38 PM

Mark305TBI

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Joined: Jul 1999

Posts: 1,431

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From: Huntsville, AL

Car: '00 Chevrolet Corvette

Engine: LS1

Transmission: 4L60E

Axle/Gears: 2.73

Power valve selection

I'm running a Road Demon carb on my 305. It idles in gear at 16" of vacuum. I've seen a couple of different methods for selecting the correct power valve. It's got an 8.5 in it, right now. is this the one I need?

Apr 3, 2004 | 11:52 PM

AM Racer

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Joined: Feb 2004

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From: Northern Illinois

Usually the choice is half of whatever your vacuum is at during idle in drive ( if auto equipped).
So close enough.

Apr 5, 2004 | 10:11 AM

five7kid

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Posts: 43,187

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From: Littleton, CO USA

Car: 82 Berlinetta/57 Bel Air

Engine: L92/LQ4 (both w/4" stroke)

Transmission: 4L80E/4L80E

Axle/Gears: 12B-3.73/9"-3.89

From http://www.holley.com/HiOctn/TechSer...o/TI-222A.html :

"A stock engine, or one that is only mildly built for street use, will have high manifold vacuum at idle speeds. To determine the correct power valve the vehicle should be driven at various steady speeds and vacuum readings taken. The power valve selected should have an opening point about 2" Hg below the lowest steady speed engine vacuum observed."