The Holley "Trick Kit" literally

LS6 Tommy

MalibuRacing Junkie
May 15, 2004
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North Jersey
RatDime said:
does anyone know what the stock boosters are on a 750 dom carb by chance? .025? I need to know front and back thanks

"Boosters" are the smaller venturi inside the main venturi that's used to amplify the vacuum signal to the main fuel circuit. They also help atomize & distribute the fuel into the air stream. AFAIK, there's only three types of booster venturii in the 4500s & they're not rated by size. There's the standard, the "long" (no longer used or available) & the annular venturi. All HP 4500s have annulars.

If by "boosters" you mean the accelerator pump discharge nozzles, they're .028" primary, .035" secondary on a standard 750 CFM 4500. I'm not sure what they are on a 750 CFM HP 4500, but they're probably smaller due to the greater sensitivity of the annular boosters.

Tommy
 

NoMoore

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May 26, 2006
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Here's something I'd like to throw out there:

Blown power valves. I have heard for years about holley's having blown powervalves, even after the blow out protection started coming in them.

I can honestly say that in my 34 years I have never encountered a blown power valve. It's almost as if it's spoke of more than it actually happens. It's always one of the first responses when someones having carb trouble, but rarely is the case!

On power valve sizing: There are a few formulas out there to help you pick the right size. (Idle vac in gear/2) or (idle vac in gear/2 +.5") Ideally you'd want your power valve to only be open when you are laying into it heavy or so I believe...

Last year I took a ride with a friend trying to see if the formula's worked, and what his car really needed as far as power valve sizing. It's a camaro with a stout 454 (850 holley), runs high eleven's on pump gas, and he drives it everywhere. So I grabbed a pen, a paper, and we ran a vacuum gauge into the passenger seat for me to monitor. Let me first say that looking down at papers and gauges while spinning on street tires in high gear is scary.

Here is the data:
Idle in gear 8.5"
cruising about 40 in 3rd gear 16"-19"
Normal driving from a stop sign 9"-14"
Moderate acceleration in 3rd gear drops to 4" and immediatly builds back up
Harder acceleration and it drops to 2"-3" and holds.
From a dead stop hell yea through all gears to 6000 in 3rd 2" the whole time.

This data tells me that the formula's would work and most likely be fine. Yet you would be able to comfortably try anything from a 4.5" up to a 7.5" to tune the opening point if needed. This could be useful if you had trouble with a rich spot under a decent load, or a sputter at a certain point. Either way it's just one more thing to think about. Knowledge is power.
 

NoMoore

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May 26, 2006
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SUMMIT RACING SUCKS

After getting the new mag (Nov-Dec 2008), I am reading through, somewhat excited that they now offer aluminum heads for those silly 409's.... Then I get to page 15 and see this gem, "Carburetor Tech." Allow me to summarize:




"The right cfm" According to Summit's take on the old formula, a 350 Chevy shifting at 6000 will run best with a 500cfm carb. I am a little unconventional on sizing so I leave this one alone.

"Flanges" "Matching the flange on the bottom of your carb to the top of your intake can be tricky." Thanks summit, I'll never buy a carb that wont bolt on to my intake again. Without you I'd be lost trying to fit a Holley carb onto an edelbrock intake.

"Metering" I don't even know where to start on this paragraph. I hope to god nobody reads this bullshit and believes it. From now on, all cars will have a 500 cfm dominator with an intermediate circuit to help it run rich under wot. Jesus, I have heard some bullshit, this take the ****ing cake. Next they'll be trying to tell me that my 5500 JW converter is tight and Stews 2500 TCI is loose(happened to a friend of mine at the store). **** SAKES.

"Other terminology"
Accelerator pump system: I'll give em that one.

Boosters: More bullshit. Not as bad as the frickin metering conundrum, but still pretty crappy. Let's take a look at the first sentence in greater detail just for fun.

"Boosters: Increase the speed of air passing through a venturi to improve atomization." The venturi increases the speed *a*holes. The booster, which also contains a venturi creates a pressure drop allowing fuel to push from the bowls into the motor. Yes you can change boosters for tuning, but if we have already established that the consumer cannot buy a carb to fit on his intake, what's the point of telling him he can tune his car by changing boosters?

"Choke" Fair enough, but your grammar sucks Summit.

"Power valve" According to Summit, "One many three-circuit carbs, this vacuum-operated valve controls the extra circuit, opening to supply additional fuel under load." "One many three-circuit carbs"? WTF is that? Oh may bad, that was a spelling mistake. No wait! A power valve is now considered a circuit? Does that mean the 3 circuit dom's are 4 circuit dom's and Holley has been naming them wrong all the time? What this boils down to is that we will begin to see people who cannot find a 650dp for their street car because Holley considers them a 2 circuit carb while Summit has invented their own metering circuit.




In summation my hatred for Summit has grown exponentially, and I am shocked to see journalism this crappy delivered to my house.
 

Redline396

Amateur Racer
Oct 21, 2008
265
1
18
clifton, nj
i am having issues with my 870 street avenger carb....it always seems to run rich at idle and at cruise speeds...i am looking to have the carb shop in santa anna,ca blue print it....has anyone here used their sevices before? i have heard alot of good things about them...............
 

LS6 Tommy

MalibuRacing Junkie
May 15, 2004
15,847
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North Jersey
Re:

NoMoore said:
I'd love to hear more about your "lazy mixing"theory with stock annular boosters. I have yet to learn much about atomization. My booster research has been pretty limited to sensitivity.

IDK what particular problems he had with annulars, but I've found sometimes annulars aren't needed for the particular application & the fuel is evaporated rather than atomized, resulting in less than optimal performance. They person tuning the car keeps richening the mains for WOT, then finds the rest of the curve is WAY too rich.

Tommy
 

NoMoore

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May 26, 2006
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Redline396 said:
i am having issues with my 870 street avenger carb....it always seems to run rich at idle and at cruise speeds...i am looking to have the carb shop in santa anna,ca blue print it....has anyone here used their sevices before? i have heard alot of good things about them...............


I have not heard anything. Pro systems and AED I believe are the current favorites.

When a carb gets silly, it's always a good thing to give it a quick rebuild and return all jetting and settings to factory. T slots, main jets, vac sec springs, idle mixture screws... and see where you are.
 

NoMoore

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May 26, 2006
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Re: Re:

LS6 Tommy said:
NoMoore said:
I'd love to hear more about your "lazy mixing"theory with stock annular boosters. I have yet to learn much about atomization. My booster research has been pretty limited to sensitivity.

IDK what particular problems he had with annulars, but I've found sometimes annulars aren't needed for the particular application & the fuel is evaporated rather than atomized, resulting in less than optimal performance. They person tuning the car keeps richening the mains for WOT, then finds the rest of the curve is WAY too rich.

Tommy
I can believe that. fwiw the TMP annular I raved about sucks.
 

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