Power Valve ?
Thread Starter
Racer
Joined: Mar 2005
Posts: 445
Likes: 0
From: SAN DIEGO(SANTEE) CA.
Power Valve ?
hOW CAN YOU TELL IF YOU'VE BLOWN A POWER VALVE(holley 4160) I just rebuilt my carb put new valve in and had a couple small back fires and then it started running bad, thought it might be the idle adjusting screws so I got new ones and installed them, it now runs a lot better, but the exhaust burns your eyes like its running rich. The screws are only ajusted out 1 1/4 turns and I don't think it should be running rich at that adjustment.
Need a little input, thanks guys
Need a little input, thanks guys
Thread Starter
Racer
Joined: Mar 2005
Posts: 445
Likes: 0
From: SAN DIEGO(SANTEE) CA.
Originally Posted by lars
Pull it out and suck on it.
Thread Starter
Racer
Joined: Mar 2005
Posts: 445
Likes: 0
From: SAN DIEGO(SANTEE) CA.
Originally Posted by Driftwood
If the diaphragm is good-- it will hold vacuum when you suck on it. I found a small leak in mine this way. I tested the new one the same way and could immediately tell the difference.
Thanks
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
If your power valve is blown - It's very obvious. Your car will be missfiring , hickuping, and farting black smoke.
I used to carry spare power valves. Tunnel rams and single planes are are easy to back fire and blow out the power valves on starting if you don't pump the gas a few times to wet everything down.
Just last year on my Demon carb I had one go bad and my vette couldn't hardly get out of my driveway to go down the street.
For 6 bucks I don't suck on gas covered items.
I used to carry spare power valves. Tunnel rams and single planes are are easy to back fire and blow out the power valves on starting if you don't pump the gas a few times to wet everything down.
Just last year on my Demon carb I had one go bad and my vette couldn't hardly get out of my driveway to go down the street.
For 6 bucks I don't suck on gas covered items.
Last edited by gkull; May 25, 2006 at 10:40 AM.
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
Yup
Your power valve will be spring loaded to one side (open). If the diaphragm is ruptured you wont be able to close it very easily by sucking on it. And judging by what you've already mentioned about instantly beginning to run crappy after backfiring, you blew your power valve. Holley Achille's heel. Also be careful retightening the new one....you can munch the gasket and it'll leak and act just like you blew the new valve
Melting Slicks
Joined: Sep 2004
Posts: 2,412
Likes: 3
Yeah, suck on the flat side. It should move the back of it towards you compressing the spring, it just moves a little bit, feel for it with your finger.
Sounds like a problem that I had with my Demon. Turned out that my squirters were too big and my PV spring was too stiff so it acted like it was blown, always open. I had 6-7 inches of vacuum and my PV was a 6.5. Changed the 31 squirters to 28s and the 6.5PV to a 4.5PV. Works great now. New carbs have had PV blowout protection for awhile, I doubt that your PV is blown.
Sounds like a problem that I had with my Demon. Turned out that my squirters were too big and my PV spring was too stiff so it acted like it was blown, always open. I had 6-7 inches of vacuum and my PV was a 6.5. Changed the 31 squirters to 28s and the 6.5PV to a 4.5PV. Works great now. New carbs have had PV blowout protection for awhile, I doubt that your PV is blown.
Last edited by enkeivette; May 25, 2006 at 09:51 PM.
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Thread Starter
Racer
Joined: Mar 2005
Posts: 445
Likes: 0
From: SAN DIEGO(SANTEE) CA.
Originally Posted by VetteLS6
ahh lose the PWR Valve put in a block out plug and up the jet sizes 3-6 and away you go.
It had a 1" spacer block under it and I removed it also.
By the way, what psi should a DP be reading? Mine reads about 7 to 9 psi, I've read that it shoud be about 5.5 but it never says if that is for a DP or a single.
Thanks
Thread Starter
Racer
Joined: Mar 2005
Posts: 445
Likes: 0
From: SAN DIEGO(SANTEE) CA.
Originally Posted by VetteLS6
Yes 3-6 jet sizes.....5-7 PSI pressure would get the job done.
Melting Slicks
Joined: Sep 2004
Posts: 2,412
Likes: 3
Booo... do it right. Keep the PV. Assuming that your carb is the same as mine the PV is a very good thing. It keeps you lean at cruise for good fuel economy and opens only when you need it to. Which is why the jets are so much larger on the secondary side (where there is no PV) than they are on the primary side (where there is a PV). It's a compensation thing. But there's no need to waste all of that fuel all of the time. Get a vacuum guage and screw with the squirter nozzles before you block off the PV. IMO.
Racer
Joined: Jun 2002
Posts: 281
Likes: 0
From: Brookfield IL
I agree to keep the PV. As long as you have a decent differential between your idle/cruising vacuum and your acceleration vacuum-- why not use it as intended? I think sometimes people read about removed PVs on racing engines (with their racing cams and low vacuum) and assume they should do it to their stock engines as well.
