Holley Power Valve
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Holley Power Valve (Eric 70)
To see if your power valve is blown just remove it and use your mouth to suck on it. You will feel the valve close. Stop sucking and it will open. You can feel the cycling with your mouth.
As for the correct value you need a vacuum gage to measure idle vacuum in gear then subtract a few inches and that is the number you are looking for stamped on the side of the valve.
As for the correct value you need a vacuum gage to measure idle vacuum in gear then subtract a few inches and that is the number you are looking for stamped on the side of the valve.
Le Mans Master
Joined: Feb 2001
Posts: 8,017
Likes: 2
From: The problem is all inside your head she said to me.
Re: Holley Power Valve (Eric 70)
Sometimes you can tell by driving it. You get a surge while crusing but taking it out is a sure way to find out and you might as will replace it then.
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Re: Holley Power Valve (Eric 70)
I asked the guys @ Demon last week how a person would know if the power valve was blown. They said that the motor would run rich all the time, that's all I could find out for what it's worth.
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
Re: Holley Power Valve (Eric 70)
Eric, a power valve adds fuel under acceleration below the throttle plates, and it is normally closed (with vacuum) at idle. If it's bad (i.e. a hole in the vacuum diaphram that holds it closed), it will add excess fuel to the intake charge, resulting in a rich mixture and the other problems you and others have mentioned. Lars (?) did a great paper on this. If in doubt, change it. It requires removing the front float bowl and metering block.
Hans
Hans
