Holley experts (Power valve)
Thread Starter
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
Holley experts (Power valve)
I can't remember on this one. I think my power valve is shot. When I cover the vent tube on the primaries it immediatly floods with fuel and shuts the motor down. As I recall this is a sign of a bad power valve. Did this about 2 years ago and I can't remember if it is supposed to flood out or just stay running. Also if it is a power valve why am I going through power valves so fast. I'm running a 6.5 valve and this one (if bad) only lasted about 1000 miles. No backfires or any bad running conditions. :confused:
I found a spare power valve and it works fine. You can hold your finger over the vent tube all day long and it runs OK. Good test for a blown power valve. Just hold your finger over it and if it stall bad power valve. Now why do I keep blowing them?
[Modified by Gordonm, 3:58 PM 4/18/2004]
I found a spare power valve and it works fine. You can hold your finger over the vent tube all day long and it runs OK. Good test for a blown power valve. Just hold your finger over it and if it stall bad power valve. Now why do I keep blowing them?
[Modified by Gordonm, 3:58 PM 4/18/2004]
Melting Slicks
Joined: Oct 2001
Posts: 2,064
Likes: 1,382
From: Halifax, Nova Scotia, Canada
Re: Holley experts (Gordonm)
Interesting question.
When I read this, I started to think, "when did I last change mine"?
It's been somewhere around 25-30 years ago.
Just a couple questions.
Are you using a genuine Holley power valve ?
Are you using any fuel additives ?
Barry
When I read this, I started to think, "when did I last change mine"?
It's been somewhere around 25-30 years ago.
Just a couple questions.
Are you using a genuine Holley power valve ?
Are you using any fuel additives ?
Barry
Racer
Joined: Aug 2000
Posts: 426
Likes: 0
Re: Holley experts (Gordonm)
I checked my Holley a couple days ago for a blown power valve using the same method of blocking the primary vent tube. It took about 12 seconds for the engine to cut out. From what I read, this proves the power valve to be OK. If it died right away then the valve would have been shot.
Thread Starter
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
Re: Holley experts (tonyk72)
Yes I am using a Holley power valve. No I am not using any fuel additives. The Holley is only 5 years old so it is supposed to be backfire proof. I don't ever remember it backfiring so I don't know what is causing it to blow. Mine flooded out immediatly when the vent tube was covered. It took about 2 seconds to die.
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: Holley experts (Gordonm)
I don't know about holding a finger over the primary vent tube on the carb to check for a ruptured power valve. To test, I remove the vower valve, push the stem end with a spring in, place the other side of the power valve on something like a smooth piece of hard rubber and release the spring end. If the stem is held against the spring, the power valve is ok. Lifting up the power valve, breaking the seal against the hard rubber surface allows the stem to jump back out, that confirms to me its ok.
Chuck
Chuck
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
Re: Holley experts (Chuck Harmon)
Putting your finger over the Holley's vertical vent tube is a quick way of determing if the power valve is ruptured and not holding vacuum. If the engine dies a few seconds of blocking off the vent it has always been my experience that it requires replacement.
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: Holley experts (70ZZ3 96LT4)
I don't doubt that puting your finger over the main vent may cause the engine to die. But how does this test the power valve? I am just thinking about all the other things that covering the main vent would do to cause problems let alone simply identify a power valve problem. I'm not trying to be argumentative. If this is a good way to tell, I would just like to know why.
Chuck
Chuck
Thread Starter
Race Director
Joined: Dec 1999
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From: Forked River NJ
Re: Holley experts (Chuck Harmon)
Not an expert but after a new power valve was put in I can put my finger over the vent tube and it does not flood out. The car runs better and idles without burning my eyes.
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Race Director
Joined: Oct 2000
Posts: 15,017
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From: central FL, near the beach.
Re: Holley experts (Gordonm)
when a PV diaphram ruptures it floods and dies. there is no other test needed. it just won't idle without turning the idle screw way in. and then only if you are lucky.
Racer
Joined: Aug 2000
Posts: 426
Likes: 0
Re: Holley experts (Chuck Harmon)
As to how blocking the vent tube proves the condition of the vent tube...I don't know the mechanics of it.
I got the PV test tip from JohnZ who I believe hangs out in the C2 section...he has never steered me wrong. :cheers:
I got the PV test tip from JohnZ who I believe hangs out in the C2 section...he has never steered me wrong. :cheers:
