proportioning valve

[JACKISBACK]

JUST WOULD LIKE TO KNOW IF I CAN USE THE STOCK ONE ? FOR THE DISC BRAKE SETUP? OR I BY PASS IT AND USE AN AJUSTABLE ONE FOR THE FRONT ? I DONT KNOW WHAT I DOING BUT IM TRYING TO DO SOMETHING .. OH YA 1971 D-100 DISC BRAKE SETUP ... THANKS GUYS

[Rodger]

Ho Ho Ho Jack

If you have added an disc brake unit in the front, you must use the proporting valvel set-up from an disc/drum unit. This is not what your truck now has.

A trip to the local pick & pull will be all you need. Or they sell new boxes with them from several venders. If you like the idea of new boxes, call NAPA first.

Rodger & Gabby
COS

[nfury8]

As Rodger mentions, the valves are specific to drum/drum and disc/drum.
Most dodge trucks with disc/drum can be used as donors. You need to pay
a little attention though, some will have 2 in and 2 out, and some will have
2 in and 3 out. In the last case, the fronts each have their own ports.
You need to match what you have, or plumb to match.

While the yards will be the cheapest option, the adjustable valves do have
some merit. The stock valves are designed to be a general guess on how
the engineers think the majority of people will have their trucks loaded.
There is an infinite amount of variables and scenarios that can play in
to the optimum proportioning. The adjustables allow you to dial in to the
perfect bias for YOUR vehicle, how it is loaded and even your driving style.
Then modify it when you change loads or modify the truck. No question
your optimal braking bias will be different with just you in the truck,
verses a load of furniture in the back or a loaded trailer behind you.

I don't have a parts book for the later trucks, but I can tell you that on the cars
Chrysler used the same proportioning valve for a Huge range of vehicles,
with very different center of gravities and bias. For example a 440 powered
Imperial totally loaded, a station wagon and a small block low option Fury
convertible would all use the same valve. I have one on my Fury dialed in for
emergency highway stops, the results are dramatically improved over the
stock valve!

[RussRoth]

I don't have a parts book for the later trucks, but I can tell you that on the cars Chrysler used the same proportioning valve for a Huge range of vehicles,with very different center of gravities and bias.

That's because most of them are not proportioning valves. I did a bit of research on this a couple years back and discovered there are actually three (3) different "configurations" one if which is basically just a T. Three different names and purposes. Some I think may have been all three in one unit and others separate but I don't remember how all that went. I don't have the information in front of me but it is in a couple FSM's I have from later rigs. Some (if not most) of the Disc brake setups didn't use a proportioning valve. I think I read that originally in one of the Mopar mags and might be why I looked it up. Those were really no different than what is used on our rigs, basically just a T.

[PatS]

Lots of good info here:
http://www.mpbrakes.com/technical-suppo ... ations.cfm

I did a disc brake conversion on a '50 Dodge car back in '95 and I had weighed the car by axle before I began and looked for a donor car of similar axle weights and found that a mid '70's Malibu was very close. I didn't want used brake parts on my Dodge so I bought a new proportioning valve from the dealer and it worked out well.

One of the key things a proportioning valve does is to put the back brakes on just a wee bit before the front to prevent diving, which was why I went with a donor of similar axle weights so this feature would work as intended. The '50 Dodge in stock form of course did not have this, so the difference in braking on that car was very dramatic.
Of course those stock brakes were garbage when the cars were new!

[Cageman]

I have never seen a proportioning valve before, must be a chevy thing, all I have seen is basically a pressure activated switch for the light on the dash. Just a T or basically a distribution block, nothing more, nothing less.
Now I have done every brake combination there is, so I think I have it figured out.
I have 4 wheel discs on my 70 w100, it has a drum T still, that was all it was, but I do have a power booster from a newer chevy truck. I have the stock chevy calipers on the front of it, and 4 piston wilwoods on the rear discs, this is probabaly the best stopping vehicle I have ever driven.
My 71 diesel dude has had four wheel drum, then front stock 78 dodge discs, then front 4 piston wilwoods and now has four piston wilwood brakes on all four wheels, with manual brakes, or a master cylinder off of a 83 diplomat. That was a power brake car originally. This thing has awesome brakes too. used stock lines and brake light switch/T.
My 69 Valiant has four wheel disc brakes, using basically the same setup as my diesel, but 73 and up Dodge front calipers and on the rear, front calipers from an 83 montecarlo. This was not the best setup, so I added an adjustable proportioning valve. A couple clicks on it and some stopping to test and it was a pefect balance. If my needs were to change, I would just have to give it a turn on the proportiong valve, but I doubt I will ever change it. I only needed the adj prop valve becuase I had a msimatch in bore sizes front to rear and to small of a master bore size.
Now my 62 with all drums, it will lock the rear up first, I would like to add an adj prop valve to it, but I doubt that will happen. All I did was add a dual resevoir master to that truck, for safety reasons. And I used a t/brake light switch off of a 68 truck I parted out. So I guess a proportioning valve on a dodge is new to me. I skipped the 70's and 80's and own a 94 and 95 dodge truck, but they have abs, and that is a whole diff story, so whatever happened from 72 to 93 is news to me.

[JACKISBACK]

THANK YOU GUYS FOR ALL YOUR HELP... JACK

[nfury8]

Pat and Cageman are correct, I should have been more specific. The valves we are general
used to are actually called COMBINATION valves, because the perform a combination of
tasks. They are routinely called proportioning valves though, and I am not really sure why
so many people (myself included) fall into calling them the wrong thing.

Generally the actual proportioning is handled at the master with variations in bore and stroke,
and there aren't that many variations either. I haven't seen a factory proportioning valve in
person, but a couple service manuals I have do show them. They are all shown separately,
inline on the rear line. Typically the combo valves are a tee with a safety light switch. Some
vehicles have metering valves for the front discs. Sometimes they are in the combo valve,
and sometimes they are separate. The separate metering valves I have seen had one line from
the tee and then the metering valve split off the 2 front lines. The metering valves holds the
fronts off slightly, since the rears have further to travel and are fighting return springs. This
helps on icy surfaces. However, not all vehicles have them, and I have read several tech editors
that say they aren't that critical. I don't have one on my Fury, I don't drive it on ice and the pads
are lasting very well.

One thing I have never understood though is that Chrysler used different valves for drum/drum
and drum/disc cars on the same year and model, even though neither had a metering valve built in.
This has always made me think there was some sort of proportioning happening, even though I know
there isn't. Many of the service manuals have cut aways, and it is obvious there isn't anything else there.

[JACKISBACK]

if i use the stock valve... do i put an ajustble one in the rear? thats what someone told me ,,, i just dont know that much about brakes... thank you guys.... jack

[nfury8]

If I follow you right, you still have the stock 71 drum brake valve, correct?

If that is the case, it should be 2 lines coming in the top and one exiting to the front and another to the rear. In this case, you can keep it and just add an adjustable proportioning valve to the rear line. I have actually been doing some extra research on a bunch of this for my C-Body site the last couple weeks. I realized that that drum brake valve used on the 69-71 trucks is the same as the drum brake cars. It is nothing more than a warning light switch. The first couple years of cars used a separate metering valve in the front lines and is how the individual lines were broke out. Around 72 the metering valve was incorporated into the tee and warning light. The metering valve was standard on the C bodies, but not on the B bodies, according to the books. All the metering valve does is hold off the front brakes to allow the rear drums to engage first. This is supposed to be for icey conditions, and offers nothing otherwise. According to RIck Ehrenberg, Mopar Action Tech Editor, the metering valve isn't really needed on a car. Not sure if that holds true on a truck.

As a side note, I was digging through my stash of parts and found a valve from a 72 Fury that actually had a proportioning valve built in. Which is bizare, because the 73 is supposed to use the same part, but the 73 part I also have doesn't have a proportioning valve included. The parts book does show that the B bodies did use proportioning though. Mopar, never say never.

[nfury8]

Quick addition to my above post. I mentioned the drum tee would have 2 in and 2 out. This is wrong.
It will have 2 in and 3 out. There will be 1 exiting the front and another the bottom front, both for the
front lines. I was thinking of when these are used for discs and an external metering valve. In that
case the bottom front is plugged, like the rear port is. I was out digging in the garage and looked at
one today.