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  Is the proportioning valve just a switch?

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Author Topic:   Is the proportioning valve just a switch?
662+2
Journeyman

Posts: 86
From: Ontario, Canada
Registered: Jan 2003

posted 01-16-2003 06:20 PM     Click Here to See the Profile for 662+2   Click Here to Email 662+2     Edit/Delete Message   Reply w/Quote
I am also putting a 74 Maverick master cylinder in my 66 mustang and a guy told me that I didn't need a proportioning valve all I needed to do is install tees in its place he said that all the proportionning valve did was if there is a pressure drop on the front or back breaks then the pressure from the high side would push a metal piece to one side and give you a reading inside the car to let you know there is a problem.

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CJ
Journeyman

Posts: 30
From: Galloway, OH 43119
Registered: Dec 2002

posted 01-16-2003 11:41 PM     Click Here to See the Profile for CJ   Click Here to Email CJ     Edit/Delete Message   Reply w/Quote
Yep, the guy is right. I personally would install the valve for safety sakes, especially if something goes wrong with your front brakes.

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steve'66
Gearhead

Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000

posted 01-17-2003 12:03 AM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
You don't need a PV.

SteveW

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69maverick
Gearhead

Posts: 897
From: Thomaston,CT.
Registered: Jan 2001

posted 01-17-2003 11:23 AM     Click Here to See the Profile for 69maverick   Click Here to Email 69maverick     Edit/Delete Message   Reply w/Quote
So are we saying that the PV only gives a signal of trouble or does it perform a saftey
task? I was under the impression it put pressure to the good side!

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Just Strokin
Gearhead

Posts: 754
From: Tuscaloosa, Alabama
Registered: Dec 2001

posted 01-17-2003 01:46 PM     Click Here to See the Profile for Just Strokin   Click Here to Email Just Strokin     Edit/Delete Message   Reply w/Quote
The early Mustangs (67's) with disc brakes, the distribution valve probably did do some proportioning, but later model cars with the distribution valve didn't. The name proportioning valve hung on and is used even today to describe the distribution valve.

The distribution valve does block one side of the brake system if there is a failure on that side (lost of pressure) and does turn on the light on/in the dash. The slide that blocks one side or the other and turns the light on is usually self-centering, but not always when repairs are made to the side with the problems. If it doesn't self center, then it has to be taken apart and manualy centered.

A proportioning valve such as used on the 65-66 Mustangs with disc brakes or the one you can purchase from Wilwood, does regulate the pressure to the side of the brake system it is installed. It does not do any safety checking or safety function in one sense of the word. The function of the PV is to limit brake pressure to the rear brakes in most cases to prevent lock-up of the rear brakes during hard or panic stops.

------------------
Larry

No fast Fords at this time but one fine cruising 96 F350 CC DRW Power Strokin diesel.
And one rusty 64 Fairlane nick-named the Rust Bucket....And sometimes called the Money Pit...

The sounds of a brain dropping into gear.....
"Buzzzzzz.......Click"

[This message has been edited by Just Strokin (edited 01-17-2003).]

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68 S-code GT
Gearhead

Posts: 1044
From: Sayreville, NJ, US
Registered: Mar 2000

posted 01-17-2003 02:39 PM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
It also gives a slight delay to the front disk brakes by allowing less pressure to them while allowing the rear drums to start moving and engage.

It proportions or regulates the pressure between the front and rear brakes.

[This message has been edited by 68 S-code GT (edited 01-17-2003).]

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Just Strokin
Gearhead

Posts: 754
From: Tuscaloosa, Alabama
Registered: Dec 2001

posted 01-17-2003 02:56 PM     Click Here to See the Profile for Just Strokin   Click Here to Email Just Strokin     Edit/Delete Message   Reply w/Quote
Most all PV's are installed in the rear brakes and no reducing of the brake pressure to the front brakes that I am aware.

This is because drum brakes are 'self-energizing' and disc brakes require higher pressures. Therefore you restrict/reduce the pressure to the rear brakes to avoid locking the rear brakes.

If you look at a DV, you can see straigh thru it from the two opposing ports for the front brakes. Gnereally on most Fords I have seen, these two opposing ports, one attackes to the MC and the other to a wheel caliper.

------------------
Larry

No fast Fords at this time but one fine cruising 96 F350 CC DRW Power Strokin diesel.
And one rusty 64 Fairlane nick-named the Rust Bucket....And sometimes called the Money Pit...

The sounds of a brain dropping into gear.....
"Buzzzzzz.......Click"

[This message has been edited by Just Strokin (edited 01-17-2003).]

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68 S-code GT
Gearhead

Posts: 1044
From: Sayreville, NJ, US
Registered: Mar 2000

posted 01-17-2003 03:14 PM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
I think that?s what I wanted to say but it came out backwards. My head is still messed up on trying to figure out another post! I can really tell by how much the spell checker is working!

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Mpcoluv
Gearhead

Posts: 945
From: Charlotte NC usa
Registered: Apr 2001

posted 01-17-2003 04:37 PM     Click Here to See the Profile for Mpcoluv   Click Here to Email Mpcoluv     Edit/Delete Message   Reply w/Quote
I have a Wilwood Proportioning valve installed under the back seeat as dipicted in the Boss 302 Chassis manual.
FIND ANOTHER PLACE to put it.
It (although it doesn't look like it) is higher than the rear calipers and is a pain to bleed.

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662+2
Journeyman

Posts: 86
From: Ontario, Canada
Registered: Jan 2003

posted 01-17-2003 04:52 PM     Click Here to See the Profile for 662+2   Click Here to Email 662+2     Edit/Delete Message   Reply w/Quote
I have disc brakes on my 66 but I am changing to a dual master cylinder so I assume that I can not use that pv that is in my car am I right?

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NoBS
Journeyman

Posts: 34
From:
Registered: Oct 2002

posted 01-18-2003 11:11 AM     Click Here to See the Profile for NoBS     Edit/Delete Message   Reply w/Quote

Hi, First post in this forum.

I've taken one or two PVs apart (none from early systems). They seem to be nothing more than an 'O' ringed spool valve that trips a switch for an idiot light if pressure is lost in one circuit.

Knowing a little about hydraulics, that spool valve isn't going to change pressures between circuits as both circuits have the same diameter pump (master) which are driven in series. Theres no true mechanical connection between the front circuit (assuming conventional master layout) and rear circuit. The rear circuits pump is driven by buildup in the front circuits pump. And since the "Proportioning Valve" is a straight through design per circuit seperated by a 'floating' spool valve, change in one circuits pressure changes the pressure in the other circuit and restoring equilibrium.

I believe the PV was an actual PV back when manufacturers used the same componants in both the front and rear of the vehicle. That was so long ago it was probably before most of us were born.

For the last couple of decades porportioning is done by componant 'sizing'. As an example the '78 Versialles I canned had 2.6 (?) front caliper pistons and the rear had 2.125 (?)pistons. 2.125 = 3.55 sq-in and the 2.6 = 5.61 sq-in. F/R = 5.61/3.55 = ~ 1.5 'overdriven' front brakes, or ~ 63% of the front calipers clamping force being generated by the rear calipers. Rotor diameter will also be a factor, but I never bothered to measure those.

When I installed the 9" I used a set of MustangII front calipers as the Versialles calipers weren't quite functional. The II front caliper is 2.6" diameter. I also installed a WildWood Proportioning valve. The brakes didn't start coming into ballance untill the WildWood was doing max reduction to the rear.

(Note: The car isn't seeing daily duty, These are test fits and proof of concept, I have to massage the assembly.)

Didn't mean to get so gabby.

PS: My Porportioning Valve is mounted by my leg on the tunnle.

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Just Strokin
Gearhead

Posts: 754
From: Tuscaloosa, Alabama
Registered: Dec 2001

posted 01-18-2003 07:20 PM     Click Here to See the Profile for Just Strokin   Click Here to Email Just Strokin     Edit/Delete Message   Reply w/Quote
NoBS,

Like I was saying, the distribution valve has been wrongly called a proportioning valve since they pretty much were first used on split systems. As stated, it serves two functions. One to shut off the leaking side of the brake system and the other is to warn the driver by turning on the brake light.

The Wilwood PV in the Tbird I had was right between my legs at the front edge of the seat. Made it handy if you need to adjust it.

------------------
Larry

No fast Fords at this time but one fine cruising 96 F350 CC DRW Power Strokin diesel.
And one rusty 64 Fairlane nick-named the Rust Bucket....And sometimes called the Money Pit...

The sounds of a brain dropping into gear.....
"Buzzzzzz.......Click"

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NoBS
Journeyman

Posts: 34
From:
Registered: Oct 2002

posted 01-19-2003 11:02 PM     Click Here to See the Profile for NoBS     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Just Strokin:
NoBS,

Like I was saying, the distribution valve has been wrongly called a proportioning valve since ... As stated, it serves two functions. One to shut off the leaking side ...(and) warn the driver by turning on the brake light.



I knew I shouldn't remove the reference to 'the afore mentioned info' in my inital post.

I could have went on a bunch more, and did. My post was quite a bit longer before editing. Only so much one should put in a post.


quote:

The Wilwood PV in the Tbird I had was right between my legs at the front edge of the seat. Made it handy if you need to adjust it.



[This message has been edited by NoBS (edited 01-19-2003).]

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Just Strokin
Gearhead

Posts: 754
From: Tuscaloosa, Alabama
Registered: Dec 2001

posted 01-20-2003 07:05 PM     Click Here to See the Profile for Just Strokin   Click Here to Email Just Strokin     Edit/Delete Message   Reply w/Quote
But, I did enjoy your dissertation on hydraulics.... ....was very informative reading....and no... ...it didn't put me to sleep

------------------
Larry

No fast Fords at this time but one fine cruising 96 F350 CC DRW Power Strokin diesel.
And one rusty 64 Fairlane nick-named the Rust Bucket....And sometimes called the Money Pit...

The sounds of a brain dropping into gear.....
"Buzzzzzz.......Click"

IP: Logged

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