Proportioning valve

Does anyone have an early style valve they want to sell? It should look like this.

I have the one shown on the webpage but it is not usable because of the pitting on the piston shaft. Also Pantera Performance has some used valves.

Mike

...FWIW, Most of us have thrown that 3 Pound piece of @#&**! in the garbage, years ago! and replaced it with a simple Brass 'T' fitting. 'IT' really does Nothing but constrict the Flow of Fluid to Both Front Calipers...

quote:

Originally posted by MARLIN JACK:
...FWIW, Most of us have thrown that 3 Pound piece of @#&**! in the garbage, years ago! and replaced it with a simple Brass 'T' fitting. 'IT' really does Nothing but constrict the Flow of Fluid to Both Front Calipers...

Thanks, I know that but I’d like to know how it was designed to work. It isn’t part of the pluming anymore and is stored with my old parts.

Mike

I recently removed the proportioning valve in my car. The front pads had 106k miles on them (yes, you read that right, 106,000 miles) and they still have about half of the lining left. This was probably due to the proportioning valve. The rears were replaced once.

Agreed! If you have fat sticky front tires the valve appears to hinder the braking benefit the tires offer. But, I wouldn’t recommend anyone modifying their braking system because of the potential liability and possible danger involved.

Mike

D'oh! Marlin Jack, you threw cash in the trash!
I'm not looking for a working valve, or even a repairable one. I plan on gutting it and using it as a tee. I like to keep things looking stock. So if someone has a 72 style valve, I would buy it.

quote:

'IT' really does Nothing but constrict the Flow of Fluid to Both Front Calipers...

I always restricted the flow to the rear there fore having full flow to the front and less to the rear .. I always thought that was the principle ? Was I wrong ???

Ron

quote:

Originally posted by accobra:

quote:

'IT' really does Nothing but constrict the Flow of Fluid to Both Front Calipers...

I always restricted the flow to the rear there fore having full flow to the front and less to the rear .. I always thought that was the principle ? Was I wrong ???

Ron

Techicaly speaking mid engine cars are supposed to have more bias to the rear of the car where more of the weight is. But us Americans is used to having most the weight up front so we like the feel of the front end bringing us to a stop. Unless you get real serious about racing, for the strret, being as you are a true blooded American, you will want your brake bias up front or it just won't feel right to you. Mid engine feel is for them there Eurpeon folk who are more sophisticated than us.

WILWOODS comments :

INSTALLATION & ADJUSTMENTS - Proportioning valves are normally installed in the rear fluid
line to prevent the rear wheels from locking before the front wheels, or to give a driver the ability to
make fine adjustments in front to rear bias percentage on the track to compensate for tire wear, fuel
load burn-off, or changing track conditions. It is generally not recommended to attempt to reduce
front wheel braking capacity.

I must have read the directions the last time I installed one.

Ron

Pantera 1887 ...here us what i found ..its really a very sophisticated valve its made to allow for load transfer and is pressure-sensitive and Master cylinder applications usually combine the proportioning valve with a pressure differential switch.

In normal braking, the poppet piston is held in a relaxed position by a large pressure spring. The poppet valve is held against its retainer by a light return spring, and fluid passes freely through the valve to the rear brakes.

In heavy braking, master cylinder pressure can reach a valve’s crack-point. The pressure applied to the 2 different areas of the poppet piston creates unequal forces. That moves the poppet piston against the large pressure spring. This action holds the conical section of the valve against the seat, which limits the pressure increase to the rear brakes.

As greater pedal force increases pressure in the master cylinder, fluid pressure rises on the smaller end of the piston. This combines with the force of the pressure spring to overcome the lower pressure now on the larger end. This forces the piston back, clear of the poppet valve.

The increased pressure now acts on the larger end of the poppet piston and again forces the piston forward to contact the valve.

When the pedal is released, the pressure of the rear brake fluid unseats the poppet valve, letting fluid return to the master cylinder. The pressure spring now returns the poppet piston to its relaxed position.

Should the front brake system fail, the warning lamp spool moves forward, taking the poppet valve with it. Pressure in the rear brakes rises and the piston moves forward but it can’t seal on the valve.

Should the rear brake system fail, the warning lamp spool will move backwards to activate the warning light. The proportioning valve doesn’t operate in this situation.

Ron

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Ron,

Thanks for the information. I think you are on the right track but the Pantera valve only has one spring.

We think (The Donut Derelicts team) the valve metering action takes place between the lower edge of the piston flange and the upper edge of the black rubber seal that you see in the picture. With the piston in the home position (up), the upper ring you see in the picture keeps the black seal spaced down a small amount so fluid can flow through the opening. The tricky part is what takes place under high pressure and how is the pressure differential created to move the piston down. Somehow the piston must move down and restrict pressure flow by closing the gap between the seal on the bottom surface of the piston. The piston is free to move down (under opposite spring pressure) because the piston shaft can move down and out the bottom of the housing. Once the seal closes pressure would be limited on the outlets. Some of the crew thought the size of the piston and the pressure drop was related to the size of the master cylinder piston and the size ratio created between them.

Mike