Holley Carb Power Valve Tuning - Summit Racing Quick Flicks

Learn how the Power Circuit plays a roll in your car's acceleration. Norm, covers all the basics on how to find the perfect tune as well as explains how the valve works.

[boostinbo]

I am really enjoying this whole series on holley carbs and I'm learning a ton. I can't wait for more!

[alanator]

Might be the best power valve video I’ve seen so far, thanks for the info Norm!

[SummitRacing]

Thank you for watching! We appreciate the feedback. Please let us know if you have any video suggestions.

[mikeasmus]

This a great video and Norm is an outstanding narrator; clear and concise.

[SummitRacing]

Dear 1109,
Thank you for the kind words. At this time we have not moved into anything regarding adjustable bleeds; we are attempting to cover the essentials for all of our carburetor lines. I hope that as we progress the opportunity to provide additional tuning insights will allow us to cover circuit modifications by using adjustable bleeds. If nothing else, the theory behind this form of tuning will provide additional insight and understanding regarding carburetion.

[davecee]

When you have a radical cam you can have a low vacuum situation then the power valves can be opening too soon causing an
over rich fuel mixture. Black smoke, (carbon in the tail pipes) a surge and fowled plugs and of fuel economy. A backfire through the carburetor can also rupture the power valve diaphragm. Further info about this is after 1992 to current,
Holley added a back fire check valve in the vacuum passage to prevent rupture of the
 power valve diaphragm . Serious drag racers plug the power valves and increase the jet size at least 6 points higher, Drag racers are not as concerned with fuel economy only ET. Great video .

[SummitRacing]

Please continue to call them like you see them; if there is something I have missed or gone astray on please let me know. Thank you.

[SummitRacing]

The logic behind this decision is the similarity in specific gravity, the nature of the petrochemicals and TEL involved in the octane increase; and the general absence of alcohol.
Let me share a thought of my own; if in doubt go fatter, add more fuel and pull a little timing out. As you tune and progress you can always bring the timing back in and tune to the proper air-fuel ratio for the fuel being used.
I hope this helps; good luck.

[SummitRacing]

The fact that the carb has sat without fuel for so long means there is a high probability that the gaskets/seals and any rubber components have dried out. Trying to reuse it now without freshening these components will most likely result in leaks and potentially a fire. We highly suggest a rebuild kit and soaking at least overnight in a carb cleaning solution to rid the carb of any varnish that may have built up over the years. Thanks for watching! Good luck :)

[GrandFunalleyMedia]

Why have I also heard to choose a power valve PV which opens 1-1/2" to 2" Hg below the minimum steady vacuum reading. Which one the best way?

[markham]

Top job Norm, very informative. Have you done any videos on the screw in air bleeds for the Idle and Main circuits yet? Cheers Rick from

[TheThirdWheel]

I installed a AEM air fuel ratio gauge it came with the weld in bung the muffler shop welded it in right in the header collector so I get all four cylinders with out it I was guessing on jetting / the easiest for me was as he suggested with idle set correct speed with eng at normal temp put it in D read vacum gauge 12 divide that by 2=6... there is no 6 so use 5.5 or whatever your reading is, I have yet to drive with the vacum gauge strapped to the wiper but with PV that is really only way to fine tune it just like a AFR gauge for jetting .

[SummitRacing]

Very important; I will assume that you are carbureted and not EFI. I have not gone the route of avgas and have generally stayed with mogas through the years. Everything I find suggests that your jet sizes will remain essentially where they are at. You might eventually see a 1, 2 or 3% change going leaner from your current jet sizes.

[kenb]

OK, to answer my own question, I watched a Holley tutorial and the 2:1 thing is the recommended power valve selection.  An idle vacuum of 13.0 inches supposedly needs a 13/2 = 6.5 power valve.  The 6.5 IS in inches of Mercury.

[mikeasmus]

Does Summit Racing Quick Flicks have any videos on Rochester Quadra-Jet carb tech/rebuilding.

[mclarpet]

Where's the Holley Ultra Dominator for these videos, they have more adjustments than you can shake a stick at ?

[oliverguyton]

I have motorcraft Holley 4180 what I like to know is what size of power valve I can put in since is a two stage

[OneEyeJay]

Hi, Wondering what Ur opinion was on cleaning the inside of the carb, short of rebuilding or a refresh kit. I have a Holley 650 double pumper 4777-4. Carb has been sitting like 7 to 8 years, It's empty now. Haven't tried to start engine yet, Wondering if spraying carb cleaner inside Vent tube to mix it with the fresh gas in the bowls while engine is running. Do U think a little bit of cleaner would ruin anything on the inside of carb?

[SickSilverado]

Very Very informative.  Great job.  This helped me so much.  Thank you.

[Clarita]

hey summit racing , i was wondering if a f150 2003 4.2 v6 can be converted into a posi trac.