Carburetor Power Valves Video - Holley Carb Tuning DVD

[stangredemption]

I know this is a way old post but Edelbrock IS a quadrajet my friend... Well based on them

[71bee383]

@stangredemption ? Edelbrock did make a Quadrajet, but they STILL make the AFB & a AVS (good ol' Carter carbs). they dis-continued the Quadraturd when they realised that they weren't selling. I would take a Thermo-quad over the Rottenchester any day of the week. BETTER fuel economy & more CFM's.

[stangredemption]

@71bee383 Good lesson learned. Tail not tucked but head held higher now LOL. Thanks for that knowledge though I needed it.

[72charger440se]

my 750 double pumper keeps flooding on me i think, it would start spitting and sputtering really bad and then it would cut out unless i floor it to try to prevent it from dying.

[2LateIWon]

So if I screw it all the way in and it still runs the power valve is broken for sure?

[ACZxGalm2]

@2LateIWon I'd assume so yes.

[88l98vette]

Great video. I have a 4160 80508 that I put a kit on because of leaking needle and seals. After the kit I am getting a pronounced stumble from off idle to full throttle only. Roll on the throttle and it's okay. I have 9 to 10 " vacuum in drive. I adjusted the accel pump as suggested but still have the stumble. The kit had gaskets, a 50cc pump instead of my 30cc, a 65 power valve same size as my old one, Any ideas.

[BoxWrench]

@88l98vette You very likely don't need that 50cc upgrade to the accelerator pump system, but you can leave it in place if you really want to.

If you just stick with the stock 30cc pump and then start with tuning the accelerator pump cams that screw into the back of the throttle lever, you may solve your issue.

You may also need to upgrage the size of the accelerator pump nozzle (squirter) to get the off-idle stumble to smooth out.

we have a video for the accelerator pump cams here at YT

[tucsondog]

Edelbrock this, holley that. The only true carburetor is a Q-Jet. Best sound, best power, best fuel economy, Period.

[kamphwagon1]

@tucsondog Yeah those ole Q jets are allright on a stock engine untill the main well plugs start leaking or the primary meterig rods start sticking ,once it's kit time for one of those there nothing but a pain in the butt... Sound dosen't make HP ,when some one can get 2hp per CID on the dyno with a Q jet like a Holley then I might take a look at one !..........

[wakawu]

Thanks for these videos, very very helpful! I had a question regarding my Holley 4160 carb. I tried tuning it the best I can with the idle mixture screws on both sides and got it to idle and startup pretty well. My problem now is when I give it wide open throttle or mash on the gas at any point I get a slight hesitation sort of a choke not really a backfire. I have to roll on the gas slowly to give it full throttle. Any suggestions?

[BoxWrench]

@wakawu

You're experiencing an "off-idle" hesitation as soon as you touch the pedal. The term "off-idle" isn't a perfect description of the problem as you and others experience the same hesitation throughout the powerband when ever you mash the pedal.

Your problem is the Accelerator pump circuit, it has tunable components. One is the accelerator pump cam, the other part is the 'primary squirter'. Just search "Accelerator Pump BoxWrench", we have a video describing the tuning here on YouTube

[kd5icr1967]

I have always devided the vac by 2 then going one step under that. Ex, 14/2=7 so I would run a 6.5. That has always worked well for me. JMHO

[BoxWrench]

@kd5icr1967

yes, you are correct in your baseline power valve tuning calculations. We have shown the same recommendation you recommend in this video... if you watch from 1:35 from this video, you will hear the same recommendation from us that you describe here.... take a vacuum reading and divide the number by '2'. If the number you arrive at is not directly available as a Holly Power Valve numerical rating, then use the next lowest Power Valve available below it, just as you suggested

[kd5icr1967]

@BoxWrench

Yea I see that now. When I watched it it triggered my memory and I just typed it out. And I just had to replace one on my carb, So I just bangged it out without watching the rest of the vid. Sorry about that

[shocktech4]

wafrederick ur on crack man.. my 350 had a 650 edelbrock on it b4, we took it to the dyno once my bowtie heads and Nx268 cam was in made just over 355 hp, we stuck a out of the box holley 650 with mechanical secondarys and it made an extra 15hp.. thats alot of hp by just throwing a carb on.. now ive replaced the base plate, and jets and it pulls harder then ever!! and i drive my 81 cutlass everyday rain or shine.. and Snow bec im from British Columbia..

[overlord1330]

wafrederick your stupid i guess that is why nascar allows afb carbs lol they dont just holley wounder why ebelb sucks

[hitace]

any vids on how to replace the holley Power Valves ?

[wafrederick]

There is one thing to do with a Holley carb,throw it away replacing it with an Edelbrock since they are only good for racing applications and are not good street carbs.Plus with a Holley,change one part and you have to change every thing.The Edelbrock is much easier to tune out of the box and the best street carb

[BoxWrench]

This is the exact response we repeatedly see from people that are not experienced with the multiple facets of tunability of a Holley carb.

It's one opinion, but we are rather experienced with Holley carbs, quite familiar with their tuning procedures (we made the video for them) and are very happy with Holley carbs in a street performance situation....especially when your engine is powered by any slight upgrade in camshaft and induction.

In many build-ups, we'll prefer the Holley...

[jayd306]

You have no clue!

[wafrederick]

All I hear people throwing a Holley carb and replacing with an Edelbrock.I heard one guy say he was going to throw one on the floor.He has a 1970 Chevy and it had a holley on it and the truck ran like crap.Runs just fine after replacing it with an Edelbrock.

[Firedogg301]

@wafrederick, Edelbrock's are very good for stock vehicles but if you race or have a performance car Edelbrock's are a piece of shit. The secondaries are impossible to tune and will bog if you step on it hard. My holly runs damn good on the street and at the track.

[JimmyK527]

mine is too and its pissing me the hell off

[carbpumper]

theres tons of vids on here just search for it

[bloozelover]

my car is pulling 20 inches at idle in gear it weighs 4350 pounds with 3.42 gears it currently has a 6.5 power valve and im experiencing a lean misfire at low rpm cruise speeds do you think that i need to run a diffrent power valve to offset the lean condition at cruise maybe a 9.5 or a 10.5 the carb is a 4175 spread bore

[BoxWrench]

first verify your plug condition to be sure the engine is in good tune. Check compression if you can to be sure. Then verify your spark and timing is good. (weak spark or non-operating distributor advance can cause symptoms)

After verifying all that, then you could begin to tune the power valve and jetting after reading your spark plugs. Jet tuning is described in our Holly Tuning DVD if you're not familiar with the process.

[ted850760]

question..can you modify an older 4150 with backfire protection to stop power valve damage,thanks for this informative tape..also do you have a chart to indicate the proper size carb for c.i. of motor ..most people tend to over carberate ..then complain of poor performance because they don't knw how to tune their fuel system

[fuzter2007]

if you haven´t backfire protection, you must use a power valve that opens early. maybe you get a little smoke on the exhaust, but is safer for the valve.

[BoxWrench]

You can get an aftermarket upgrade kit that will allow you to drill into your throttle body carb base and install a power valve protector. The part is available at Summit or Jeg's.

Also, go to Holley's website and use their "carburetor selector" to run through and find the right CFM rating for a carb for your engine type.

[moparniac]

Quiktree from moparts will diagree with this method...

[BoxWrench]

This method was designed and is recommended by Holley factory technicians for setting baseline power valve range. It will set a good starting point for anyone to begin further tuning from.

If others disagree, it would likely be that they have another method for tuning for race or performance.

Using a vacuum gauge to determine what the internal vacuum pressure of the engine is at idle is the most accurate way to set your baseline before tuning for higher performance.

[skirkland1980]

thats why you cant build a race engine with " off the shelf " parts, most parts will need to be modified to run correctly.

[elcaminomann]

You guys are very cool, I can tell you spend a lot of time and money to do these videos....Thank you for your time and information....

[jknig31]

good to know info.

[zrocwd]

good video