To Remove the Proportioning Valve or Not to Remove the Proportioning Valve? That is my question…

 Proportioning valve was designed for a stock car. You no longer have such a critter so remove it. If it is still working it is not working in harmony with your current configuration. 

 Keep the shuttle valve after a thorough cleaning. It is still a somewhat effective safety device. 

 As for the aftermarket proportioning valve I will defer to others wiser than me. 

Larry 

The OEM proportioning valve lowers pressure to the front calipers, in an effort to improve brake bias front to rear. Once removed, you'll have full pressure to the front calipers but your braking bias will be even more to the front than before. Putting an adjustable proportioning valve in the rear circuit isn't necessary with stock rear calipers as there's zero chance you'll want to reduce brake pressure to the rear calipers. 

Steve Wilkinson explained to me that it is not a proportioning valve and instead is an anti-chatter valve for the front rotors.  Thus removing it will not change front to rear proportioning.  He also explained that removing it definitely helps the braking system because the valve usually traps air resulting in a spongy brake peddle.  Removing it is accomplished with a tee that the vendors can provide.  The tee has the correct threads and bubble flares.  Alternatively, the valve can be gutted and then it functions as a tee.  Once gutted it does not trap air.  Here is one that I recently gutted:

David Nunn is absolutely correct. The question is IF you have upgraded your rear Calipers. If the answer is no then DO NOT remove the stock p-valve. If you have an upgraded rear Caliper then by all means, removed the p-valve. 

Someone said you don't have a stock car so remove it. But I think you said your brakes were stock. What isn't stock is you have bigger rear tires. That doesn't help the situation, it makes it worse. You have more braking potential in the back than you did when the car was stock. So improving the fronts by removing the P-valve will also cause the back to be less effective. 

We have done lots of testing to prove this theory. People still want to debate it but this issue has been tested and there is no question that a car with stock rear Calipers will have better braking performance with the valve in.

Those that claim their cars braking was better with the valve out and stock rear brakes are likely incorrect. It may feel like the fronts are stronger at the expense of the rears doing almost nothing. Measure actual braking distances and you will find a stock braking system is better balanced with the p-valve in place.

Scott

By the way, the shuttle valve does nothing for safety other than turn the dash light on when the brake pressures are unequal (front to rear and before the p-valve). This is totally unnecessary since you will immediately know (by brake feel) that there is a problem with either the front or the rear brakes if that situation were to occur.  

“Anti-chatter valve”

🧐🧐❓

 I have never heard of such a brake system component.

 A Google search finds nothing called an anti-chatter valve. 

 I did find an anti-shudder valve but that is for diesel engines, to shut off air to the cylinders to prevent shut down run on. 

 The Pantera technical manual refers to that component as an “equalizer”. 

 On Steve’s website it is referred to as a “pressure control valve”. 

But “anti-chatter valve “??

Nope. 

A proportioning valve by any other name is still a proportioning valve.

My 2¢

Larry 

Could it be that it is a "two-stage" proportional valve in that it allows full pressure when brakes first applied and then reduces pressure under hard braking?

(the reason he reffers to it as anti chatter.)  

I thought I read of a low pressure check valve could be used to keep the pads near rotor drums (NOT PANTERA) to improve response and thus maybe anti chatter

I gutted mine, but I did it because the instructions from SACC restore said do it when I changed to Scott Bells Wilwood kit. The kit I used was just under 2000$ and it used the stock calipers, I got the seperate park brake too. The kit was an easy install and works perfect. The calipers are balanced so no need for the propertion valve.  When I get hard on the brakes from speed, the car just stops with no tire sliding or lockup.  I went through several sets of used calipers before i bite the bullet and did the KIT. I am glad I did, NOW my car will roll, before, there was always some drag from the old calipers.  https://www.saccrestorations.n...ton-w-parking-brake/ 

Thanks for the responses, everyone. Interesting discussion. So interesting that I've decided to simply R&R the brake master and leave the brake-related gizmos in place until the time I upgrade to a SACC brake kit.

Enjoy, 

Ron

Wilkinson's explanations certainly made sense to me.  He also added that most people mistakenly call it a proportioning valve.  As pointed out above, his website calls it a Valve Assembly Pressure Control.  The valve does not have any connection to the rear brake line and thus lacks the ability to function as a front/rear proportioning valve.  All three connections are only front brake lines. Again, Wilkinson explained that the valve's purpose is help reduce chatter on the front brakes when the discs become warped.  It may be best to call him for more details.

The two valves that I gutted were quite frozen up.  After nearly 50 years they were no longer functional due to corrosion and hardened rubber parts. Thus, as I mentioned earlier, gutting or removing them is appropriate.  There is no rebuild kit for them and they tend to be an air trap.

These are some notes I made for myself as I seem to forget a LOT lately

the hydraulic arrangement (or 5177)

and how I think the pressure control valve works

the link at the bottom is where I purchased rebuild kits ( I have yet to take apart original)

...A Lot of Theory going on Here. I only deal in Proving the Facts!

First, the Shuttle valve does a lot more than Just turning on a Light!! The first time You Blow a Brake Line, You'll Know, It just saved your Life, by Closing-off the Damaged System (Fronts or Rears), and Leaving the Remaining Operating System, to Fully Function.

The 'Proportioning' Valve Limits the Pressure to the Front Calipers, It is My Opinion, By Test, Remove that 2 Pound Piece of Junk, and Throw it as far as you Can into the Dumpster!! Just by doing That, Your Front Braking has Improved. The Photo of the Rear Brake (4-Piston Superlites, 12.5 x 1.250 Rotors), was taken After I Returned from My trip to the Deserts. There are Approx. 3000 Miles on this Rotor. They are Polishing-In, Perfectly. On the Front Brakes, I installed Scotts' 6-Piston Calipers on (Pantera East) Thicker, Vented and Cross-Drilled, Rotors. By Installing the 6-Piston Calipers....Perfectly, This alone, Increases Pressure to the REAR Calipers!!

The Truth is...I have Done Brakes and Custom Machined Brake Installations for Over 50 Years! These 6-Piston Calipers are the Finest, most Responsive Brakes I have ever Experienced! The Most Tight, Up-to- the Top, Pedal. Smooth Solid Pedal Feel. You Actually 'Receive' MORE Braking 'Action', Than You 'Ask' For!! I have Never Experienced Breaking Action as This, In ANY Vehicle. They Bring My Pantera Down From Speed....FAST, but Smooth! And when you Come to the Actual, Final STOP, You Experience That Wonderful, One-Single, 'Lamborghini', Blip, of the Nose. You Only get this 'Jounce' with Stiffer Aftermarket Shocks, But, It Takes the Calipers to Perform it. It's the 'Last Millisecond of the Rotor Being 'Locked' to a Stop!' 

For a 'Road Car', the Pad Compound is PERFECT! They wear-in Fast and Smoothly, I have Yet to Hear a Single 'Squeal'! I Do Not have a Photo of the 6-Piston Installation, Yet.

Last, Notice the Rear Calipers have been relocated Forward of the Half-Shafts. And, the SACC Parking/Emergency Brakes Have Not been installed yet. Most All Exotic Cars have all 4 Calipers Mounted Closest to the 'Center of Gravity'. This Decreases the 'Polar Moment of Inertia', as well as just being a better Engineered use of the Physics of it All! 

...Stay with the Stock Brakes?? Fine, if You just drive to the 'Grocery Store', once a Month; or Your Pantera just sits in the Garage, and You come out and Look at It every once in awhile! But! IMO, You will NEVER Know What You are Missing!

But, if Your into 'Spirited Driving', and Breaking Speed Laws, Once in awhile….Get New Brakes. I will 'Bet My Pay-Check', You'll be Happy You Did!

For the Road, These are the BEST by TEST!! 

Good Luck with it    

I have a 100% factory original brake set up on my 73L with 30 K mi. I drove it over 800 mi since july getting used to the car. I have pushed it hard over 100mph  for many miles In very hot July aug to see how it preforms A, it never over heats with stock radiator, B it brakes fantastic at all speeds, never heats up or looses pedal In fact my 46 yr old suspension is still like new. I build and restore all type of cars and I can tell you once you change any component from the factory set up you will end up changing many component's. My 69 Camaro SS for example came with new front discs and I have been chasing a RF wheel lock up for 5 years. changing out every component to no avail some things twice. To solve the problem I added an adjustable valve to one wheel and it finally solved the problem.