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1/12/2018 9:57 AM  #1


Proportioning valve

67 fastback   289 4 speed.   I am installing 4 wheel disc brakes.it was drum front and back.do I need a new proportioning valve.or will old one work.thank you

 

1/12/2018 10:46 AM  #2


Re: Proportioning valve

4 wheel drums did not have a proportioning valve,its a distribution block.
MS sells this one that you use to replace your distribution block, it includes the proportioning function as well.
https://www.mustangsteve.com/pv-100-proportioning-valve-instructions/

Last edited by 50vert (1/12/2018 10:47 AM)


"Those telephone poles were like a picket fence"
 

1/12/2018 3:57 PM  #3


Re: Proportioning valve

Ditto 50vert


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

1/16/2018 5:49 PM  #4


Re: Proportioning valve

Is it necessary to have a proportioning valve with 4 discs

     Thread Starter
 

1/16/2018 7:15 PM  #5


Re: Proportioning valve

351c wrote:

Is it necessary to have a proportioning valve with 4 discs

No two cars are the same. There might be one specific combination of front/rear weight bias that would function well or even perfectly without a valve, but I believe I would want an adjustable valve so it could be dialed in for the particular car.
I have a Versailles valve on my 66, and it has served well, but could probably be better.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

1/16/2018 10:50 PM  #6


Re: Proportioning valve

351c wrote:

Is it necessary to have a proportioning valve with 4 discs

What MS says is generally true from my experience.  However, while I was trying to figure out why my GT 12.5" fronts and my Explorer 11.5" rears discs did not seem to work very well I gutted the fixed proportioning valve and let the system operate with the same line pressure on front and rear.  Subsequently I determined that I was only producing 9.5" of vac and 750 line pressure.  I traced that to too much cam at 6000 feet.  Then I added a vac pump and got nearly 1400 line pressure on the front and rear.  Apparently I hit the magic mix because I have lock-up tested it and the fronts will lock before the rears and that has to be due to the differing rotor size and the difference in swept area.  So it can be done but I certainly start with an Prop valve.  Nice thing about the fixed valves is that they have a differential pressure switch built in that can turn on a brake trouble light and save half of the system should you have major leak.

 BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

1/17/2018 3:03 PM  #7


Re: Proportioning valve

I installed 4 wheel discs Cobra 13/11inch on my 67 FB... stopped great w/o any proportioning valve...just used original drum/drum plumbing , rebuilt of course.......you want the rears to grab before the fronts....if not add a proportioning valve ..jj 

Last edited by jerseyjoe (1/17/2018 3:12 PM)


"Never put a question mark where God put a period "  Richard Petty
 

1/17/2018 4:17 PM  #8


Re: Proportioning valve

jerseyjoe wrote:

......you want the rears to grab before the fronts....if not add a proportioning valve ..jj 

Huh?  One of us is bass akward, Joe.  In my 'sperience if the rears lock first the hiney is very apt to pass the front due to loss of traction.  If the fronts lock first you can't steer but the traction of the rear tires keeps the thing more or less straight.  At least that's what I've been told and what I have felt in the seat of my drawers.

BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

1/17/2018 4:27 PM  #9


Re: Proportioning valve

Bullet Bob wrote:

jerseyjoe wrote:

......you want the rears to grab before the fronts....if not add a proportioning valve ..jj 

Huh?  One of us is bass akward, Joe.  In my 'sperience if the rears lock first the hiney is very apt to pass the front due to loss of traction.  If the fronts lock first you can't steer but the traction of the rear tires keeps the thing more or less straight.  At least that's what I've been told and what I have felt in the seat of my drawers.
BB

You got it backasswards...lock up the fronts and you have uncontrollable steering and the back end whips out of control ...think of it as a motorcycle going 55 mph and you grab only the front brake hard 

Last edited by jerseyjoe (1/17/2018 7:56 PM)


"Never put a question mark where God put a period "  Richard Petty
 

1/17/2018 11:06 PM  #10


Re: Proportioning valve

jerseyjoe wrote:

You got it backasswards...lock up the fronts and you have uncontrollable steering and the back end whips out of control ...think of it as a motorcycle going 55 mph and you grab only the front brake hard 

Okay, thanks for straightening me out.  Butt, I'm still a bit confused.  You say if the rears don't lock first one should install a Prop valve.  But the prop valve is installed in the rear line...always...and can only reduce the line pressure which would make the rears lock after the fronts have caused nose dive and weight shift.   Hmmmmm?

BB

Last edited by Bullet Bob (1/17/2018 11:09 PM)


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

1/18/2018 1:01 AM  #11


Re: Proportioning valve

I wish MS would "un-Ban" Barnett..........he'd clear this up for everyone.....

 

1/18/2018 2:38 AM  #12


Re: Proportioning valve

josh-kebob wrote:

I wish MS would "un-Ban" Barnett..........he'd clear this up for everyone.....

Yeahh Yeahh!  ..... go ahead and laugh ..... You know where he ended up.
Still plaques me.
Guess I'm the exception to the tolerant Ozzie rule.


 


"Those telephone poles were like a picket fence"
 

1/18/2018 6:59 AM  #13


Re: Proportioning valve

I'm gonna ask Richard...I usually encounter him at least once a day.

BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

1/18/2018 10:47 AM  #14


Re: Proportioning valve

I was 10 years old when my dad taught me to drive. We had a bunch of different cars and trucks. As I got old and "bolder" and knowbody was looking I would love to slam on the brakes in the pickups and try to keep the rear end behind me. The front brakes would always lock up first and the rear end would swing around depending which way the wheel was turned. It was great in the 53 GMC not so in the Model AA. I guess more than anything that was because of weight distribution but the point is the front brakes would allow / cause that to happen.


70, ragtop 351W/416 stroker Edel Performer heads w pro flow 4, Comp roller 35-421-8. T5
 

1/18/2018 2:15 PM  #15


Re: Proportioning valve

The purpose of a proportioning valve is to adjust the balance until the fronts and rears lock at the same time, giving you the maximum amount of control of your vehicle.

The following applies only to four wheel discs.
First, you must have an adjustable proportioning valve to the rear brakes. Next, adjust the valve to maximum pressure reduction to the rears. It is best that you do this by gauge, not by guess. Next, on your lonely test road perform 60-0 stops, opening the prop valve one turn at a time until you get the rears locking up first. Then close the prop valve one turn and you should be balanced.

If you fail to lock up the rears first, even with full brake system pressure, your rear brakes are too small, or your rear tires are too big. If the rears always lock up and the fronts never lock, the rear brakes are too big or the rear tires are too small.

One final comment: if your vehicle routinely locks up either the fronts or rears under anything less than full-panic-we’re-all-going-to-die braking, then you have a brake system imbalance that needs correcting. As suggested in the previous paragraph, correcting may involve replacement of the brakes themselves to achieve balance. I remember looking at the rear calipers on my Taurus SHO thinking they were rediculously tiny, but the vehicle braking was excellent and well balanced.

 

Board footera


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