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Holley power valve?
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Author:  Jeb [ Thu Jun 24, 2004 7:42 pm ]
Post subject:  Holley power valve?
Exactly what is the Holley power valve that everybody talks about and what is its purpose. And does the Holley 1945 on my car have one?
Author:  GunPilot [ Fri Jun 25, 2004 7:30 am ]
Post subject: 
The power valve serves to introduce about ten jet sizes' worth of fuel into the intake when vacuum falls low enough to allow it to open. It is normally spring-loaded open, and vacuum holds it closed when the engine is running.

At WOT or when there's low vacuum and the engine is pulling air, the spring overcomes the vacuum diaphragm and opens a couple ports to allow a big shot of fuel to be drawn into the engine. The idea being the engine is under load then, and needs enrichment.

Power valves come in a variety of settings to tune how soon they open. A PV marked 65 opens at 6.5" Hg.

Image

I'm not real familiar with the 1945, but I'd say no. The only 2bbls that have them, I think, are the ones with the metering block similar to the 4 bbl Holleys (the 5200 series?)

Hope this helps.
Author:  Dennis Weaver [ Fri Jun 25, 2004 9:01 am ]
Post subject: 
All of the Holleys I have worked on, one, two and four barrel have a "power valve" (or "economiser") of some sort, not necessarilly like the one pictured for a 4150/60 four-barrel.

The one and two-barrels (excuse me for not remembering all the Holley model #'s) have had a plunger arangement in the top-half of the carb that depresses a valve plumbed into the main well in the bottom half which enriches things in the same fashion as described by gun pilot. These are modulated with vacuum through either a piston similar to a Carter metering rod piston, or, in the case of the 1920 one-barrel, a rubber diaphragm (Holley seems to have had a fetish for rubber diaphragms...). All modern carburetors I have dealt with have some means of enriching the mixture under load, Holley just employs a real stupid (my opinion) way to do it. :roll: :twisted:

D/W
Author:  mnecaise [ Fri Jun 25, 2004 9:04 am ]
Post subject: 
The 1945 has a power valve; but, it's nothing like the one pictured (which is for a 2300 2bbl or 4150/4160/4500 4bbl). They're built into the carb bowl -- if you look you'll see a brass screw in plug with a rod sticking out of the top of it. The rod has a very light spring behind it... That's the power valve in a 1945. Mounted in the airhorn is a vacuum operated piston that will depress the plunger in the power valve if vacuum drops.

The power valve in a 1945 isn't subject to the "blown diaphrams" you might have heard about. The pictured valve uses a rubber diaphram that was subject to being ruptured if the engine backfired. BTW, Holley fixed this years ago by putting check valves in the carb, between the power valve and the manifold vacuum source.
Author:  panic [ Fri Jun 25, 2004 10:47 am ]
Post subject: 
Author:  Dennis Weaver [ Fri Jun 25, 2004 11:54 am ]
Post subject: 
Quote:
BTW, Holley fixed this years ago by putting check valves in the carb, between the power valve and the manifold vacuum source.
...They only had to "fix" it because it was such a poorly conceived design to start with.

I see that the 1945 has a power enrichment circuit pretty much exactly as I described above, thanks for clarifying. :)

D/W
Author:  Dennis Weaver [ Fri Jun 25, 2004 11:59 am ]
Post subject: 
Quote:
Carter's advantage is that the main jet changes both to more or less the same degree with 1 change, and you can also change either one with the rod, but the vacuum setting is less precise.
Perhaps, but it is still adjustable with different springs which are a cake-walk to change. :D

D/W
Author:  Jeb [ Fri Jun 25, 2004 3:47 pm ]
Post subject: 
Would somebody tell me why Holley's Carbs are so complicated on the inside. When I rebuilt the Motorcraft 2-barrel on my truck, it had very few parts and I had it rebuilt within an hour. But, the Holleys I have worked on (4-barrel off of a Ford 390 & the 1945 on my uncle's D-150) have a zillion parts. I mean, the 1-barrel had more parts than the 4-barrel ! Thanks for telling me waht a power valve is. Just wanted to know what that thing was everybody talks about(now I know :D )
Author:  Dennis Weaver [ Fri Jun 25, 2004 4:51 pm ]
Post subject: 
You think THAT'S sumthin'...

You oughta rebuild a Mikuni carburetor off an eightysomething Mitsubiscuit motor... Less Parts in the Space Shuttle, I believe.

Just face it, Holley's are a lot like Chevies... You can get them to work, but they still suck! :shock: :twisted: :lol:

D/W
Author:  Dartvader [ Fri Jun 25, 2004 6:42 pm ]
Post subject: 
My sentiments exactly! I've wasted alot of money on Holleys over the years. I am a slow learner. I will not use one now, and I do have a car left with a carburetor.
Author:  Jeb [ Fri Jun 25, 2004 7:37 pm ]
Post subject: 
How come chrysler never built a carb, like ford did? I have rebuilt one carter 4-barrel for a friend and it was super easy. Now I see whay these things are so popular.
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