How to reference your power valve for supercharged engines - Ford Muscle Forums : Ford Muscle Cars Tech Forum
 
LinkBack Thread Tools
post #1 of 7 (permalink) Old 02-05-2008, 11:50 PM Thread Starter
Tech Contributor Gold
 
Join Date: Nov 2006
Location: Wasilla, Alaska
Posts: 742
How to reference your power valve for supercharged engines

I am by no means an expert on carburetors. Recently I have taken on an engine build of my lifetime. As this build progressed, I have learned about things I have never even heard of. One of these things is "referencing the power valve." The power valve in your carb operates on vacuum, or should I say a lack of vacuum. Blower carbs are available and already have the power valve referenced. I had already purchased mine before knowing anything about this so I tackled this as part of my learning curve. This project was a crash course for me. All the info in this article has been gathered on various web sites and tech boards. To the best of my knowledge it is correct. If anyone can add or correct me please feel free.
A referenced power valve carburetor is intended for use with superchargers, and have the capability that allows their power valves to reference the intake manifold vacuum below the supercharger. This will allow the power valve to operate as it is designed, based off intake manifold vacuum. A power valve provides further enrichment to the main metering system under load (low vacuum) conditions. Without this external referencing, the power valve would be "reading" the Supercharger boost pressure, which has no bearing on the engine load.
The following was taken from Holley's tech site:
Nothing will kill a blower or Nitrous engine quicker that a lean condition. You want plenty of fuel available for the engine to use .There is a thing you need to know about the power valves on a roots style blower engine. The power valve is installed to keep the engine from loading up and running rich at an idle. On a normally aspirated engine the engine vacuum at idle will hold the power valve closed. When you step on the gas the throttle plates open and the engine vacuum drops as you accelerate. When the vacuum drops below the rating of the power valve , it snaps open and richens up the main system. On a blower with the carb mounted above the rotors there is constant vacuum all the time even under wide open throttle. The power valve will never open and you will have a lean condition. To remedy this there is a modification you can have done that is called manifold referencing the power valve. You plug the vacuum feed hole in the baseplate for the power valve. Then you drill a hole in the side of the main body into the hollowed out vacuum chamber for the power valve. You then insert a vacuum nipple in this hole. You will run a vacuum line to the lower intake manifold from the new vacuum nipple. Now you will have vacuum on the power valve at an idle, and when you hit the gas as the boost builds, it will force the power valve to open and richen up the main system. This can be done by most carb modifiers or even yourself.
--------------------------------------------------------------------------
Step 1.Find the power valve port. This base plate is a ProForm. This is a Holley design and should be very similar if not exact depending on the model. Overall, the end result will be the same.

-------------------------------------------------------------------------
Step 2. Drill out the brass insert and remove the check ball ( power valve protect models)

-------------------------------------------------------------------------
Step 3. I used a wood screw with coarse threads to remove what was left of the insert.

-------------------------------------------------------------------------
Step 4. Remove the check ball. As noted above, these are on Power valve Protect models. This ball prevents blowing your power valve in the case of a back fire.

-------------------------------------------------------------------------
5.

-------------------------------------------------------------------------
Step 6. Drill the baseplate. Make sure you drill the baseplate low enough so it doesn't interfere with the metering block. This is very important! I chose to use a 3/16" brake line as a vacuum tube. I purchased it at NAPA for a few bucks and it already has a flare to help hold the vacuum line on. I pre drilled a pilot hole before drilling the 3/16" hole. I drilled on an angle as seen to miss the screw hole.

-------------------------------------------------------------------------
Step 7. Plugging the power valve port at the bottom of the baseplate. I found an old lead shot shell for my donor. I punched one lead shot down into the hole and swaged it into the port blocking the bottom of the hole. I added one more on top of that to plug a hole that was made when they machined the baseplate( when they drilled the screw hole they got into the power valve port).

-------------------------------------------------------------------------
8. Another view of the swaged lead shot protruding from the hole.

-------------------------------------------------------------------------
Step 9. 3/16" tube inserted. Apply two part epoxy on to tube then tap in. Blow into new vacuum line to clear epoxy from port. Any excess will blow out of port.

-------------------------------------------------------------------------






Now it is possible for me to run my power valve off of manifold vacuum.
I hope someone can benefit from this article. I only wish I had found something like this before I started all my research (head banging and many unanswered questions). Thanks FordMuscle for this website and allowing all of us to share. Now go bang some gears!
Attached Thumbnails
Click image for larger version

Name:	gal1.jpg
Views:	10532
Size:	15.1 KB
ID:	3044  

Last edited by FATNFAST; 02-06-2008 at 07:38 AM.
valleyfirearms is offline  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old 02-06-2008, 05:42 AM
Registered User
 
Join Date: Oct 2004
Location: Bethesda, MD
Posts: 1,564
Re: How to reference your power valve for supercharged engines

Hey, that looks just like my engine before I dropped it in! Good write up on the power valve referencing. I will also add that on an engine w/ a blower adding jet extensions on the secondaries if you are using a double pumper also helps to keep the motor fed when you go into boost -Mike
Attached Thumbnails
Click image for larger version

Name:	1018.jpg
Views:	8066
Size:	56.4 KB
ID:	3046  

Last edited by FATNFAST; 02-06-2008 at 09:09 AM.
blown68 is offline  
post #3 of 7 (permalink) Old 02-06-2008, 09:28 AM
Subscriber
 
Join Date: May 2003
Location: Maine
Posts: 1,369
Re: How to reference your power valve for supercharged engines

I gotta say that you did a really nice write up and the picture quality is 2 thumbs up. Thanks.

6.29 @ 112 MPH 1.48 60'. Home-fabbed twin turbo 302 at 3242 lbs. Fastest ugly Mustang on FM!
james302 is offline  
 
post #4 of 7 (permalink) Old 02-06-2008, 12:10 PM
Registered User
 
Join Date: Nov 2002
Location: Lancaster Oh
Posts: 296
Re: How to reference your power valve for supercharged engines

Nice write up, it just shed some light in my eyes

1992 mustang lx coupe, caged, mini tubbed, 393 with Novi2k supercharger 15lbs of boost, BS3 EFI . 9.12 @149
mrtbolt64 is offline  
post #5 of 7 (permalink) Old 02-06-2008, 06:31 PM Thread Starter
Tech Contributor Gold
 
Join Date: Nov 2006
Location: Wasilla, Alaska
Posts: 742
Re: How to reference your power valve for supercharged engines

Thanks for the kudos guys. Sometimes it's hard to put thoughts into words but I did the best that I could. At first it is somewhat difficult to grasp but after researching and understanding what the power valve does and how it operates, it is easier to understand the process of referencing manifold vacuum to the power valve.

Hey Blown 68, sweet engine!
valleyfirearms is offline  
post #6 of 7 (permalink) Old 02-06-2008, 10:55 PM Thread Starter
Tech Contributor Gold
 
Join Date: Nov 2006
Location: Wasilla, Alaska
Posts: 742
Re: How to reference your power valve for supercharged engines

Thanks Blown68, Another item I never knew about. And I know I'll need them with that blower! I just purchased a set of jet extensions and a notched float off e-bay for a total of $24.50 shipped. I love this site!
Quote:
Originally Posted by blown68 View Post
Hey, that looks just like my engine before I dropped it in! Good write up on the power valve referencing. I will also add that on an engine w/ a blower adding jet extensions on the secondaries if you are using a double pumper also helps to keep the motor fed when you go into boost -Mike
valleyfirearms is offline  
post #7 of 7 (permalink) Old 03-18-2008, 03:13 PM
Registered User
 
Join Date: Mar 2008
Location: royal oak, mich
Posts: 28
Re: How to reference your power valve for supercharged engines

Interesting to say the least. This issue was never done at Holley from an engineering aspect. Tons of aftermarket applications but I never saw this done. I'll have to check out their website. I lost a lot of interest in them after they laid us off. I would suspect this could be done to an Edelbrock carb too considering vacuum controls the step-up rods for enrichment.

02 F-150 that just LOOKS stock,Trans shift kit,4.56 gears w/ Detroit TruTrac, LiveWire Pro Racer Package tuned. My baby: http://i48.photobucket.com/albums/f240/kaboom10/100_0291.jpg
kaboom10 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Ford Muscle Forums : Ford Muscle Cars Tech Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
9" axle reference needed. v8shadow All Ford Techboard 3 06-05-2007 11:56 AM
Sealed Power Piston Number Reference Question! Galaxie_406 All Ford Techboard 18 06-14-2005 09:30 PM
V-2 Vortech Supercharged 32 Valve 5.4 in 02 \'Stang thecarphotoguy1 The Garage 0 04-04-2005 09:35 PM
supercharged 393- Where is my power going? luebben All Ford Techboard 21 06-14-2004 07:30 PM
Recommended Reference Manuals 4drbronko Torino Pages 1 02-20-2003 03:30 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome