holley carbs
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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
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.
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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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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Then I have the only HP's ever built with dual power valves. Humm, go figure!
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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1,277 Posts
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).
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 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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I wonder why they need to change back and forth?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).
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.
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!
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.
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.
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