Disc brake proportioning valve

[aqmet]

I am converting the front brakes on by 64 D100 Town Wagon to disc Brakes using the Scarebird brackets, I will be also changing out the master cylinder to a dual resivior (disc/drum) type for 72 d100. My question is if the M/C is for a Disc/Drum setup will I also need a proportioning valve.

Mike

[Hobcobble]

I am converting the front brakes on by 64 D100 Town Wagon to disc Brakes using the Scarebird brackets, I will be also changing out the master cylinder to a dual resivior (disc/drum) type for 72 d100. My question is if the M/C is for a Disc/Drum setup will I also need a proportioning valve.

Mike

Welcome to the site Mike. Just so folks know.... are
you talking manual disc/drum brakes?
John

[aqmet]

This is a manual master cylinder, maybe in the future i will look at a power booster.

I also noted that I posted this in the wrong section is there anyway I can move it to the brake section.

Mike

[dahooligan]

I did this on my 63 D100 nonpower.Just added disc kit and master cylinder but no proportioning valve.I plan to add rear disc kit so will put in proportioning valve then.I bought a Willwood valve from local racecar shop,around $45............pat

[PatS]

[jimmy]

Yes you need a proportoning valve, All disc/drum set up has them or needs them. Disc brakes require much more pressure than drums, if you do not use a proportoning valve the rear will lock up very premature. Especialy on wet or dirt roads.

Please don't think of not useing a valve it can be very dangerious!

[aqmet]

Thanks to everyone for the information, I found a five port proportioning valve, it seems to be based on the GM valve similar to what Pat described he used. I am collecting the parts and plan on getting to the installation in a month or so, I'll let you know how it goes.

Thanks
Mike

[nfury8]

Welcome!!

In a nutshell, no. Chrysler rarely ever used a true proportioning valve on any of their
vehicles, trucks included. A proportioning valve limits the psi to the rear brakes.

Chrysler usually handled this by balancing the size of the front and rear brake components.
The only time a proportioning valve should be used is if you are having issues with the rear
brakes locking up before the fronts, or you are running 4 wheel discs. The master cylinder
plays a large role also. Calipers require a lot more volume, compared to cylinders, which
is why the master cylinders must always be swapped.

Typically what you will find is a Combo valve, which will include a distribution block,
warning light switch and sometimes a metering valve.

Chrysler hasn't used residual valves for over 20 yrs. When used, they were screwed into
the ports of the master. However, they changed the design of the wheel cylinders in the
early 80's to include a spring for this function. ALL aftermarket wheel cylinders will have
this spring. So if the wheel cylinders have been replaced in the last 20 yrs, you should have
the spring. If not, I would highly recommend spending $20 and replace them!

Metering valves were sometimes used to delay the engagement of the front discs to allow
the rear drums to energize. This is because the drums move the shoes much further away
from the drums than the pads move away from the rotors. This however is only done to
help when braking on ICE and I have read multiple articles, including those by Mopar Actions
tech editor, that say the metering valves really aren't big of a deal and most vehicles will
be just fine, even on ICE with out them, as long as you drive appropriately for road conditions.

So I say NO, because the combo valves really do nothing but provide a warning light when
the pressure on one fluid circuit is higher than the other. In which case I usually know there
is a problem before the light comes on any way! Also your 64 wouldn't of had this light anyway.
So really, you can just run the rear line straight the rear axle and the front line into a $2 brass
tee to break out the front lines. Unless, your axle already has a splitter like the rears do at
the axle.

If you do decide you want a combo valve, you can pull one off just about any Mopar, since the
functions are all the same. Some will have one output to the front, which will then need split,
others will have 2 for the front.

[CSS-Registry]

i used a combination valve from a 1985 D250 pickup. i mounted it down in the frame in front of the removable auto trans member and behind the main crossmember that is torched on auto-matic D100's.



it gave me dual ports for the front and a single port for the rear.

in light driving (no windshield yet) the backs tend to lock up first. i will see what happens when the front pads seat in a little more before i add a proportioning valve.

a dual pot master cylinder made for discs is a must. the bigger pot is for the front calipers.

to keep the master from leaking all over the place i learned a tip from Ron aka "68fish" on one of these sweptline forums:

take piece of 80 grit paper and lay it on your work bench grit side up. before adding fluid invert your rebuilt or new master and "face" the top sealing surface by sanding it top side down on the paper. this will keep the metal from gumming up the works and will reveal any potential leaks - i also stuffed each pot with a wad of masking tape sticky side out. after i got the surface good and level i cleaned it with brake cleaner and then painted it so it wouldn't rust while under the hood. it has been over a year since i did it and it still look like this:



Ben

[RussRoth]

nfury8 is spot on with his information. Good job!

[aqmet]

Thanks for the information – I have another question regarding the tubing from the master cylinder.

The tubing to both the front and rear wheels is 3/16”. In looking at the mating surface inside the outlets of the MC I’m not sure if they will seal a 3/16” flare. Does anyone know if they will or will I need to use some type of reducer?

[nfury8]

Are the threads different size? If the threads and the seat are both larger, it probably needs
1/4" tube.

I have seen some strange combinations used. Sometimes the tubing is the same size and
just different nuts. But sometimes it will use different tubing also.

For example, the 94 master and valve I am using uses 3/16" tube from the master to valve
on the front discs, but 1/4" between them on the rear rear drums. 3/16" is then used on
both circuits from the valve to the axles. No idea why??? Can't see how it would have any
impact, since the lines down the body are all the same diameter.

With all that said, hopefully someone with first hand knowledge of a 72 will chime in.

[aqmet]

The front and back outlets of the master cylinder have different size threads; the pot for the front discs is ½-20 and the rear is 9/16-18. I understand they did this so that you couldn’t hook up the lines incorrectly. I believe you are correct that the tubing size is not critical since they all eventually end up at 3/16”. The ½-20 and 9/16-18 tube nuts are available for both 3/16” and ¼” inch tubing, so I think it comes down to what size tubing will seal on the seats, anyone know this?

[nfury8]

If the seats in the ports are different sizes, then I would guess 1/4" on the larger and 3/16" on the smaller.
The seats on mine were easy to tell the size difference.

[chilort]

I wish I would have known all of this. I had a splitter valve deal on my '68 and when I went to disc on the front I thought I needed to install a different disc/drum splitter. I drove it for a long time with no problem but found a disc/drum splitter on an '82 or so in the junk yard. I thought I had to have the newer splitter so I got it. I had a lot of trouble finding all the fittings I needed to make it work. If I would have known this I would have left it alone.

[nfury8]

That is unfortunate, you were probably fine. The up side is that you probably have
a metering valve now. While probably little need for it in GA, it will not hurt.

For reference, here are some cut-aways.

A regular splitter with warning switch, what would have come factory on dual reservoir,
drum/drum vehicles. Port configuration may vary slightly.


Same valve as above, but with a metering valve and a different port configuration.
The 45 degree ports and protruding stem valve are tell tale signs of a metering valve.
Although some will have one of the front ports blocked and then split with a tee on
the front axle. Operation is still the same.


If someone were concerned and really wanted a metering valve, early 70's cars
sometimes used a separate metering valve mounted on the frame rail, behind
the front left tire.