drum brake proportioning valve

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Silent Thunder

Silent Thunder

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I converted my 64 Valiant from a single master cylinder to a dual. All four wheels are drum as from the factory. When I step on the pedal I have to stand on it to make the car stop. Many have said I need a drum brake proportioning valve or do I need residual pressure valves? I thought many here on the site said it was not needed. Brakes all the way around are good almost new. I feel as if I am not sure the car will stop I have to push so hard. Thoughts??
 
maybe you need a master cylinder with smaller bore
a smaller master cyl piston will increase pressure with less pedal force
....1" usually works best on manual brakes.
 
If you were putting discs on the front then you would need a proportioning valve for the rear drums.
 
I bought the master cylinder that was recommended for my car from folks here on the site. I am not putting Disc on the front. What I read it seems as if drum/drum systems need residual pressure valves to keep back pressure on all four drums? Any one know more about this? Here is some info:

Residual pressure valves are required for the proper performance of your braking system. There are
two different residual pressure valves with different ratings:
10 lb: A ten pound residual pressure valve is needed to the drum brake portion of your brakes to maintain
a firm pedal. The springs in the drum system will pull the drum brake shoes back in away from the
drums. The residual pressure valve maintains a pressure in the system to counteract the spring tension.
This allows instant activation of the drums giving a firmer pedal.

HOW DOES THE VALVE WORK
The residual pressure valve has a one way “duck bill” valve inside which allows fluid to pass in one
direction freely while restricting the flow in the other direction. The spring inside will hold a residual
pressure to a certain point and then release above that maintaining the calculated residual pressure.
To install the residual valve into the line, cut the line and re flare both ends
with a double flare. Install and tighten.
Fluid freely passes this way
Master side Brake side The one way valve prevents fluid from passing back until the
spring tension is overcome and reverse flow can occur.
Depending on the spring rating this will be either 2 lbs or 10 lbs
pressure. The valve will then close once this level is reached
keeping the residual pressure on the other side.
 
when switching from all drums from a single resivoir master cylander u need a proportioning valve that goes with it i am planning on doing the swap myself i grabbed the master cylinder and proportioning valve in one peice off a 75 dart
 
63VALIANT*KISS said:
when switching from all drums from a single resivoir master cylander u need a proportioning valve that goes with it i am planning on doing the swap myself i grabbed the master cylinder and proportioning valve in one peice off a 75 dart
Click to expand...
I think your right but thats a distribution block and not a proportioning valve. My Dart was four wheel drums with a duel master. When I went front disc brakes I kept the distribution block and had to add a rear proportioning valve.

http://inlinetube.com/Prop Valves/pro_valves.htm
 
What is the new master cylinder for? Did you do anything else with the brakes? Have you checked to see if a wheel cylinder is frozen and not applying both sides?
 
If it is a master cylinder for drum brakes it will have the residual check valves in it already.
 
chryslerfat said:
What is the new master cylinder for? Did you do anything else with the brakes? Have you checked to see if a wheel cylinder is frozen and not applying both sides?
Click to expand...

New master cylinder is because I went from single to dual. Brakes function fine other than hard pedal with a excessive travel. I think I need the valves to place the 10 pounds of back pressure on the system.
 
Silent Thunder said:
New master cylinder is because I went from single to dual. Brakes function fine other than hard pedal with a excessive travel. I think I need the valves to place the 10 pounds of back pressure on the system.
Click to expand...
If it a master cylinder for a 4 wheel drum brake car it already has the valves in both sides. The 1st thing I would do as long as its the correct master cylinder check to be sure your wheel cylinders dont have frozen pistons. If it is for a disc drum combo it wont work correct in your system.
 
I installed a Wagner MC71258 dual master cylinder. I believe what I need is 4 residual pressure valves to maintain 10 pounds of pressure on each wheel cylinder.
 
Silent Thunder said:
I installed a Wagner MC71258 dual master cylinder. I believe what I need is 4 residual pressure valves to maintain 10 pounds of pressure on each wheel cylinder.
Click to expand...


Why not just crack the brake lines nuts loose and see if oil squirts out--if so it has pressure in the line

You might have a disk-drum master, I got no way to loo up the part number, maybe somebody else knows

If it does seem like each line has pressure--oil squirts out all four lines near the wheel cylinders, I would crack open each bleeder screw and let in dip bleed for awhile--while topping up the reservoir. Maybe there is air in the lines ?
 
Silent Thunder said:
I installed a Wagner MC71258 dual master cylinder. I believe what I need is 4 residual pressure valves to maintain 10 pounds of pressure on each wheel cylinder.
Click to expand...

I just googled it and it came up with 2 different options
option 1 was power drum brakes /w 1 inch bore
option 2 was manual drum brakes with 1 inch bore 67-68
but that only showed up in pre 69 models.
you could have a power drum brake master cylinder.
 
I just converted my 65 to a duel master for a 67 Dart with manual drums. But I have never herd of this 10psi for drum brakes. News to me. And I sure do not understand why you would want that. Would that not make the brakes drag? I tore apart the factory original single pot cylinder and I saw no form of check valve at all. And I know there is none in the distribution block. And the brakes worked just fine. Sounds to me like you still have air in your lines, or have a disc brake master. But I am no expert. LOL
 
No they would not drag. 75 pounds are required to activate brake shoe presure. Most master cylinders have this built in. Its a rubber boot where the master cylinder piston goes in from the brake pedal.
The master cylinder I installed was a part number I was given from this site. If that is wrong (for power brakes) then is there a better number I should use? I want to buy new.
 
It is not the wrong one. Power and manual drum brakes used the same one. It is the disc brake master that is deferent. I used the same master as you, only a deferent manufacture (looks identical). The pedal pressure seems the same as it was with the single cylinder. It takes a lot of force on the pedal with ether in my car to stop it. But every manual brake car I have owned seemed that way. I guess I am just to accustomed to mushy power brakes on these new cars LOL
 
a residual pressure valve is used with drum to keep the wheel cylinders from leaking fluid
the way it works is by maintaining a small amount of pressure on the seals so they stay expanded, without this pressure the seals in the wheel cylinders can sometimes contract enough to leak
modern wheel cylinders have a spring in them that presses on the seals and serves the same function as a residual pressure valve

proportioning valves are used with front disk, rear drum setup's in order to maintain proper front rear brake balance, they are not used with 4 wheel drum brake applications
on a 4 wheel drum brake, dual reservoir setup you only need the proper distribution block

I would check that your brake shoes and drums are clean and properly adjusted
1: with the wheel on turn the adjuster through the slot in the backing plate so that when you spin the tire by hand it will not spin more than 1/2 rotation when you let go

it is also possible that the master cylinder was mislabeled or defective, this happens quite frequently with re manufactured parts
 
Silent Thunder said:
New master cylinder is because I went from single to dual. Brakes function fine other than hard pedal with a excessive travel. I think I need the valves to place the 10 pounds of back pressure on the system.
Click to expand...

1 The valves or lack of, have no bearing on the current problem

2 Your statement about "excessive travel" is OPPOSITE of what you should have if the master cyl. is "too big," causing harder pedal compared to old master.

SO.................

Did the brakes work "better" before you switched the master?

Did you do ANYTHING else, IE replace shoes, turn drums, replace wheel cylinders, etc, when changing the master?
 
A Residual pressure valve is generally only used where the master is low in the car (I.E. frame mounted in a Hot rod ) to prevent bleed back.
 
Residual valves are for hotrods that have the master cyl mounted on the floor, did you get a new distribution block with two inlets one for front and one inlet for rear, also will have two outlets. The old one for the single only has one inlet with two outlets (basicly just a tee). You do not need a proportioning valve on 4 wheel drums, only a distribution block.
 
Tincup said:
A Residual pressure valve is generally only used where the master is low in the car (I.E. frame mounted in a Hot rod ) to prevent bleed back.
Click to expand...

crlush said:
Residual valves are for hotrods that have the master cyl mounted on the floor, .
Click to expand...


This seems to be a trend passed around the www but the fact is that for YEARS manufacturers used residual valves, and long after 67 when they went to tandem cylinders. I'm not sure I understand why they were used if not needed, because as we all know, manufacturers are not known for adding stuff that isn't needed.

I think we are focusing too much here on the presence / lack of a residual valve. I don't believe this issue has beans to do with the problem
 
crlush said:
Residual valves are for hotrods that have the master cyl mounted on the floor, did you get a new distribution block with two inlets one for front and one inlet for rear, also will have two outlets. The old one for the single only has one inlet with two outlets (basicly just a tee). You do not need a proportioning valve on 4 wheel drums, only a distribution block.
Click to expand...

No what I did was use the existing "T" in from the master cylinder and then plugged one hole and the two remaining went to the left and right front. The rear line goes to the axle and is then split with the existing block to the left and right.
 
That is what I did. Sounds like we have the same distribution block. But with one exception. The rear port on the master cylinder should go to the front brakes, and the front port to the rear brakes. Not sure if it really mater's on a 4 wheel drum car or not. But that is the way I have always seen them hooked up.
 
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