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Discussion Starter #1
i just picked up a holley ultra hp 850. let me first say, this is one NICE piece, if it performs half as well as it looks and is put together, this thing should fly, lol

this is the first carb i've used that has a secondary power valve. does the standard powervalve tuning techniques still apply? can i still use the rule of thumb where the starting powervalve size=(idle vaccuum reading)/2? any tricks and/or tips will be helpful for sure!
 

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Long Live The King
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If it's a drag car, street/strip take it out and up-jet 4-6 jets.

G
 

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Hemi's ROCK!!!
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That is a good starting point. There is also more info on this on Holley's Tech page in the FAQ section fo the Carburetor section.. :cool:
 

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Long Live The King
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lol, i know that if i take it out, i'd need to plug it. but i think there is more tunability with the powevalve in the back as well as the front.
What linkage does the carb have: Progressive or soft progressive?

G
 

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Long Live The King
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:) I figured you did...lol. When you've been around as long as I have though; you see a lot things go down. ;)

I bet you have.................

I can just hear it now" ............well you didn't say it needed to be plugged "

G- ;)
 

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Discussion Starter #9
What linkage does the carb have: Progressive or soft progressive?

G
hmmm...not sure. i've not made the distintion yet, lol. at the moment, i only know of progressive, or 1:1, i didn't know there were subtypes of progressiveness, lol.

picture:
 

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Long Live The King
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^^^

Soft progressive starts to open the secondaries somewhere between 1/8th and 1/4 throttle. Progressive starts to open the secondaries at 1/2 throttle. For a street car the progessive is a huge fuel saver because the engine will rarley see more than 1/2 throttle you'll spend 80% of the time in the primaries.


Crack the throttle linkage and get back to us.


G
 

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Discussion Starter #11
ok, in that case, it's Progressive. it's also setup so i can go to 1:1 easily. it is a street/strip car. only comes out on nice weekends, or going to the local index races (average about 10 weekends a year). gas mileage isn't a huge deal, but i know it will come as a by-product of proper tuning.
 

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The problem with a PV in the secondarys is fuel running away from it when launching. I have read of the PV extension, but have never used one. I run a plug on drag applications.
 

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Thread killa
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This is how I tune my pv, I was told it is a switch and you can time when you want it to come in, since vacuum holds it shut I put a vacuum gauge on the engine and drive it, then look at the reading say every 1000 rpm and graph it, if you know what your cruise vac reading is you can put in a pv to open below that so when you are cruising the valve is shut but when you get on it, the valve opens. food for thought.
 

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If it's a street strip car run it progressive and plug the rear PV. There are no extensions for the PVCR's so they can become uncovered on the initial launch. Don't need to chance running lean. 1 to 1 linkage will make it SEEM more responsive, because you will open more throttle area with smaller throttle openings, much like that famed one hole carb advertizes... In reality with a drag car you run wide open all the way down, and on a foot brake car you might find it easier to keep a consistent stage RPM with progressive linkage.
 

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Those carbs kick ass but just a warning they have some guerilla at the factory put the jets in. They are in tight. I know of a couple of people that have broken the jets trying to get them out. I used a massive flat blade to get mine out and they did not break but they were about to when I used my jet tool.

jmarkaudio I am sending you a pm. I have questions.
 

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If the jets are stuck, heat the metering block before you try to remove them. Usually, the hot water faucet is enough but a propane torch or an electric heat gun and some pigskin gloves will do it if more heat is necessary.
 

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Hemi's ROCK!!!
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My 750 HP's are mounted sideways, so I don't worry about running lean on the rear bowls. Another thought..... :cool:
 
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