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Discussion Starter · #1 ·
do the 4 corner idle adjustable carbs use a secondary power valve . or is it blocked off
 

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Yes, and YES, depends.. if new.. two Power valves installed, used? maybe and maybe not....
 

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Discussion Starter · #3 ·
do i have to run two power valaves .will it run ok with only a primary p.v.
 

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The basic DP's (sold today) with 4 corner idle only have one power valve. IE: http://holley.com/types/Double Pumpers.asp

The "HP" 4150 series carb do have dual power valves and 4 corner idle and a lot more options. http://holley.com/types/4150 HP Series.asp

The older Standard DP's 4150 series IE: 0-4776-1. 0-4777-1. 0-4777-3. 0-4779-2. 0-4779-3. 0-4779-4. 0-4779-5. 0-4779-6. 0-4779-7. 0-4780. 0-4780-1. 0-4780-2. 0-4780-3 carbs do not have 4 corner idle but do have dual power valves. The older DP units with "LIST" numbers also have dual power valves.

Al
 

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Yeah I have some older 4779s that have two power valves. They all used to. I still have one I bought brand-new in 1977.

None of my HPs came equipped with secondary power valves. I've never seen an HP with a secondary power valve (and I've seen a lot of them). Holley first started adding 4-corner idle about 15 years or so ago. Carb shops had been performing the modification before that though.


I don't think any of the performance Holleys come equipped with secondary power valves anymore.
 

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Discussion Starter · #8 ·
i have a profrom main body and base plate the base plate is drilled for the secondary fuel metering this why i wanted to know if i could or should use a secondary power valve the stuff was given to me so this is what i have to use thanks
 

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Yeah I have some older 4779s that have two power valves. They all used to. I still have one I bought brand-new in 1977.

None of my HPs came equipped with secondary power valves. I've never seen an HP with a secondary power valve (and I've seen a lot of them). Holley first started adding 4-corner idle about 15 years or so ago. Carb shops had been performing the modification before that though.


I don't think any of the performance Holleys come equipped with secondary power valves anymore.
Then I have the only HP's ever built with dual power valves. Humm, go figure!:rolleyes:

I have also seen a lot of people who think they have "HP" carbs that do not!

The HP & DP carbs are differant

Al
 

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Whether you need to use the pv or not is specific to the engine. I do not run any pv's in my carb, but that does not mean anything. You will have to experiment. I tried running a pv in the primary side and I could not get the engine to keep from getting a lean miss right before the secondaries opened. The only way was to make the jets too fat and therefore when the pv opened it was way rich.
 

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All right Al, here's the scoop. I called the Holley tech line (and man was I on hold for a long time to get through).:rolleyes:

I finally got to talk to a person and asked him about the HP Series and the secondary power valve. He told me that all of the earlier HP carbs did not come equipped with a secondary power valve. It wasn't until a couple years after the dash one models came out (numbers with -1 after them) that they came with rear power valves. He says that all HPs now being manufactured have secondary power valves. So you must have a new or newer -1 model.

Like I mentioned earlier, I haven't bought a new one in a couple years now but the last one I got from Summit still did not have a secondary power valve. I usually block the secondary power valve anyway but I guess Holley got enough requests from their customers that they finally decided to offer the provision on their newer carbs. I still have a Holley HP 750 that I bought in the early 90s the day they were released for sale. I remember how excited everyone was that Holley decided to produce them.
 

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All right Al, here's the scoop. I called the Holley tech line (and man was I on hold for a long time to get through).:rolleyes:

I finally got to talk to a person and asked him about the HP Series and the secondary power valve. He told me that all of the earlier HP carbs did not come equipped with a secondary power valve. It wasn't until a couple years after the dash one models came out (numbers with -1 after them) that they came with rear power valves. He says that all HPs now being manufactured have secondary power valves. So you must have a new or newer -1 model.

Like I mentioned earlier, I haven't bought a new one in a couple years now but the last one I got from Summit still did not have a secondary power valve. I usually block the secondary power valve anyway but I guess Holley got enough requests from their customers that they finally decided to offer the provision on their newer carbs. I still have a Holley HP 750 that I bought in the early 90s the day they were released for sale. I remember how excited everyone was that Holley decided to produce them.
I wonder why they need to change back and forth? :rolleyes:

They spend a lot of money for changes when they would make more just leaving the them alone!

"Funny", I have dual PV's, guess what! The secondary's are now blocked! Funny Hu!:D

AL
 

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Nobody's mentioned typically needing to go up 8-to-10 jet sizes when the PV's are blocked to make up for the lack of the PV enrichment.:no:

I agree, I don't run them in the rear either.:no:

I figured I'd just throw that out there so someone doesn't build a carb that goes WAY lean at WOT and can't figure out why.:D
 
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