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Old 04-30-2010, 02:11 PM
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Choosing a powervalve

How should I go about choosing a power valve?
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Old 04-30-2010, 02:31 PM
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I usually take my vacuum at 800 R.P.M's and divide that in half .
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Old 05-03-2010, 06:36 PM
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I checked the vacuum with the car in gear and it was bouncing around between 6 and 7 inches. If I have a 6.5 power valve is that ok or do I need to go a lower? If is bouncing between 6 and 7 inches is there a possibility that my power valve is open when it is idling.
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Old 05-03-2010, 07:25 PM
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You usually want to go 2 inch's below that reading. So 6.5 with your gauge, I would go to a 4.5 power valve. Ken
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Old 05-03-2010, 07:26 PM
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put a 4.5" power valve in it. You want the power valve to stay shut at idle.
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Old 05-04-2010, 01:31 PM
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Quote:
Originally Posted by 406MOUSE
I checked the vacuum with the car in gear and it was bouncing around between 6 and 7 inches. If I have a 6.5 power valve is that ok or do I need to go a lower? If is bouncing between 6 and 7 inches is there a possibility that my power valve is open when it is idling.
What are the engine and cam specs?

I would be looking closely at the whole deal to see if I could get the idle vacuum up from where it is- 6 to 7 in Hg is in the range of a pretty "big" cam, duration and overlap-wise. So unless the cam IS big, there could well be ways to increase the idle vacuum and the idle quality and off idle response along w/it.

Last edited by cobalt327; 05-04-2010 at 01:39 PM.
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Old 05-04-2010, 01:37 PM
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As Cobalt kind of eluded too, make sure your carb and ignition is properly tuned before reading your idle vacuum. That is a prett low vacuum, not too bad, and there are a lot worse out there, but with that low of a vacuum I'd maybe go with even a 3.5". If it is however more around 10" then a 4.5" would be fine, perhaps too small but it will help fuel economy.
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Old 05-04-2010, 04:40 PM
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need lots of timing at idle with a cam that big (7 inhg vacuum). at least 20 degrees at a 1000 rpm idle.
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Old 05-05-2010, 11:17 AM
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Yeah right now my car is idling at a1000 RPMs.
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Old 05-05-2010, 08:06 PM
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Quote:
Originally Posted by 406MOUSE
Yeah right now my car is idling at a1000 RPMs.
when you increase the base idle timing, you can readjust the carb idle speed screw to get the idle speed back down.
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