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Old 06-01-2013, 03:38 PM
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Power Valve

Hi,

Is the power valve system and subsequent fuel delivery strictly affected by vacuum?

Holley's website recommends keeping the number low to ensure the powervalve does not kick in at idle but I didn't think power valve's came into play at all in the idle circuit?

Thanks

Gary

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Old 06-01-2013, 03:55 PM
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Ya they do. Especialy on a auto trans application when idling in gear.
The power valve does effect the idle circuit which gets its fuel from the main circuit, which is feed by the PV and main jet.
a manual trans car is no so critical at idle. as the idle vacuum is higher and no engine load at idle.

at idle if /when the power valve is open,, the emulsion mix of the fuel in the idle circuit changes.
More liquid fuel of the total volume.
If the power valve is open at idle and the engine idles in gear for a extended time the plugs soon foul.
Keeping the power valve closed at idle keeps the plugs clean.
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Old 06-01-2013, 03:59 PM
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For must rumpity rump street machine ---street strip cams a 4.5" power valve gets it done.
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Old 06-02-2013, 06:47 PM
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power valce

Thank You F-BIRD'88,

When I ran through the testing here is what I came up with:

@ 35 mph steady drive (1700 rpm), flat road - 17 hg
@ 50 mph steady drive (2100 rpm), flat road - 16 hg
@ 65 mph steady drive (3000 rpm), flat road - 13 hg
In park idling - 14
In drive idling - bounces between 9 and 14
Accelerating agressively (but not WOT), ie. to over take a car from going 50 mph - 10 hg

so my first thought was that I should go with a 11 PV to a) give me more power when overtaking and b) that this is 2 below the 13 I'm getting so about correct.

The odd thing is that quickfuel only provides, at the highest a 10.5, so 11 is out of the question; next you are saying I need to actually go lower to a 4.5.

So, my question is; is a PV only intended to be for WOT additional power or also for heavy acceleration?

I think I need to do some more runs and include grades in these to see where the vacuum level is then.

Gary
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Old 06-02-2013, 06:54 PM
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You want to go with1/2 of whatever your lowest vacuum is . In your case a 4.5 will work fine for you. Higher and valve will open creating a rich condition at idle.
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Old 06-03-2013, 06:21 AM
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In drive idling - bounces between 9 and 14

This is not a radical cammed motor.


The car will be fine with either a 6.5" or a 10.5" power valve. pick one.
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