Proportioing valve vs residual valve

[KULTULZ]

I know this is a little late but while CAROUSING WITH MY BROWSER, I came across this post which was overlooked at the time -

So if I understand this thread correctly, the proportioning valve doesn't really work? I see the adjustable ones working for race applications only. I understand the theory-which is why I ordered one along with a new Master from a 69 mustang-all OEM styles. So should I not bother with the one I bought?

Mike

Mike,

Your application is a 1957 FORD with four wheel drum and you just wanted to go with a split system (DUAL CIRCUIT MC), correct (if you still frequent here)?

There was no PROPORTIONING VALVE (PPV) used on this period DRUM-DRUM FORD car. The only valve used on a 69 MUST DRUM-DRUM (other than RESIDUAL PRESSURE VALVES located in the MC outlet ports) was a PRESSURE DIFFERENTIAL VALVE (PDV) which appears in appearance similar to a period PPV for a DISC-DRUM application. It's only purpose is the allowing of a WARNING LAMP to be displayed if there is a pressure failure in one or both brake circuits and as a brake fluid DISTRIBUTION BLOCK.

The correct PN for your application would be C8ZZ 2B257-B. One should be found either NOS or take-off and rebuild kits are available - (shown in 1st attachment)

If you are not worried about a possible functioning split system after hydraulic failure on one circuit and/or a WARNING LAMP, you would just plumb the MC into the system without a PDV.

A PRESSURE DIFFERENTIAL VALVE is shown in the 2nd attachment. It is shown within a COMBINATION VALVE (2 or more valves within one body) so don't let it confuse you. When hydraulic pressure is lost in one circuit, the pintel will move causing the WARNING LAMP to illuminate.

Now as for the MC. It's being an aftermarket and most likely off-shore, if it does not have RESIDUAL PRESSURE VALVES (RPV) in the line outlets, you will have to plumb them in separately after the MC.

Hope that made sense ...

[59meteor]

Having the "pleasure" of having to drive OE factory vehicles with no brakes, due to rusted lines, blown wheel cylinder/caliper, or a torn flex hose, although the brake warning light in the dash did indeed come on, I certainly did not need a warning light to let me know of the malfunction. It was very obvious when the brake pedal went all the way to the floor, with zero back up braking provided by the PDV. For what it`s worth, so far I have put over 3000 miles on my 59, with front disc, rear drum, manual brakes with a dual chamber master cylinder and an adjustable proportioning valve, and no PDV, and the car stops just fine, including 100 MPH 1/4 mile dragstrip passes at a track with a short shut down area, varying road surfaces, down hills etc. Your mileage may vary.

[KULTULZ]

It was very obvious when the brake pedal went all the way to the floor, with zero back up braking provided by the PDV.

The PDV is not designed to do what you want or expect. If one circuit goes bad, the pintel shifts (to the failed circuit) to illuminate the lamp and (depending on type of failure) hopefully allow there to be one safe stop to get the car off the road. The valve is designed to give the driver warning of a failure but of course a drastic system failure is another situation.

Now there is (or was) a PDV that did block off the failed circuit but I have never come across one on a FORD.

As for your DIALING-FOR-HOPEFUL BRAKES VALVE use, you have just not have come across the right situation yet. It is designed for track use only.

Is it cold up there yet? It is going to be 67F here tomorrow ... 

[gasman826]

There is no set rule how these valves work.  Different years, different makes and different models worked differently.  Confusing...damn sure is!  This discussion has left out the master cylinders.  The front and rear on most (NOT ALL) produce different volume to the front and rear brakes on disc/drum systems...thus the front and rear port designation on the master cylinder.   The proportioning valve finishes up the bias by regulating pressure to the rear brakes.  Since the proportioning valve is not adjustable, the manufacturers have selected a safe rear bias for the worst conditions.  So, a huge portion of most driving under utilizes the potential of the rear brakes.  I had a Suburban that had 95/5% front/rear bias.  It didn't stop, wore out the front brakes and the rears were still good at 150k miles!  But it was safe.

I run disc/disc with no proportioning valve.  The master cylinder is one dual/tandem Wilwood.  I also have Wilwood manual adjustable bias valves but the valve is always adjusted wide open.  I drive in all conditions except snow/ice...not due to concerns over the vehicle braking abilities but to salt.

[KULTULZ]

There is no set rule how these valves work.  Different years, different makes and different models worked differently.  Confusing...damn sure is!  This discussion has left out the master cylinders.  The front and rear on most (NOT ALL) have different size bores to produce different pressure/volume to the front and rear brakes. 

Well, there is a set rule, but car manufacturers don't release that info. They build for a completely stock vehicle the valving being at a fixed rate and don't want enthusiasts messing with factory settings or they may be held liable in court.

If one decides to modify his vehicle, it (valving-MC choice) should be done in a thoughtful manner and that would include a skid pad.

As for the MC, most everything has one bore size and must be matched to the application. The only thing I have come across with differing bore sizing is STEP-BORE MC's where one bore is used for circuits with low drag calipers.

ABS solved all of this.

[KULTULZ]

... and no PDV ...

THE PDV was dictated by FEDERAL SAFETY STANDARDS in 1967 with the introduction of the dual circuit MC.

If you don't want or need the warning lamp, then there is no need. I personally want it and a hand-brake warning lamp as I am forgetful (read old and ugly).

Actually if you think about it, when that pintel moves, it opens the other circuit to the leaking/failed circuit. Kinda scary when you think about it. That lamp is there to inform the uneducated driver that the system senses a pressure drop and to take it in for service.

When you were a LINE-TECH, and a complaint came in with bias problem(s) (pre-ABS), how did you handle it?

[59meteor]

Frankly, in the 35 years that I worked as a dealership mechanic, I can not recall ever having anybody complain about brake bias issues, unless there was a hydraulic or mechanical fault (ie , collapsed flex hose, seized caliper or wheel cylinder, park brake system, frozen caliper slide(s) etc). As for the in dash warning light, if the brake pedal pedal goes all the way to the floor, I don`t need a light to alert me that there is a problem! Same as I don`t need a light to inform me that my gas gauge is near the "E" mark, or that there is no passenger in the other seat. As for weather, here in Nova Scotia, we are currently sitting at about 38F, and next week should be in the high 50s-low 60sF. But back near Vancouver BC where I previously lived, they are having lots of snow (after the major rain fall and flooding a month ago, and well below freezing.

[KULTULZ]

There is no set rule how these valves work.  Different years, different makes and different models worked differently.  Confusing...damn sure is!  This discussion has left out the master cylinders.  The front and rear on most (NOT ALL) have different size bores to produce different pressure/volume to the front and rear brakes.

I want to make sure I am reading this correctly. Are you describing different cylinder bores within one MC or different MC bore sizes for different applications. 

I run four wheel disc with no proportioning valve.  The master cylinders are dual Wilwood.  I also have Wilwood manual adjustable bias valves but the valve is always adjusted wide open.

If you are running dual MC's (I think that is what I am reading), there is no need for an ADJ BIAS VLV on the setup as they (MC's) are adjustable aren't they?

Just trying to make sure I read your post correctly. CRS is cutting in ...

[KULTULZ]

Let's try this again -

Frankly, in the 35 years that I worked as a dealership mechanic, I can not recall ever having anybody complain about brake bias issues, unless there was a hydraulic or mechanical fault (ie , collapsed flex hose, seized caliper or wheel cylinder, park brake system, frozen caliper slide(s) etc).

The usual driver/customer will not likely have any idea how automotive braking works. It is up to the TECH to diagnose and correct.

Your description was a catastrophic failure. Was the cars yours or a customer's?

As for the in dash warning light, if the brake pedal pedal goes all the way to the floor, I don`t need a light to alert me that there is a problem!

And neither does the customer. Did this car have a functioning PDV?

A PRESSURE DIFFERENTIAL VALVE (mandated by FEDERAL REGULATIONS in 1967 on new cars only) gives the driver a WARNING (hopefully) of a SERVICE FAILURE (real or impending) within the system and should give the driver, if there is a failure,  enough time and stoppage to pull the car over and call for a tow if inadequate braking is noticed. It DOES NOT have to be used in a RETRO-FIT although the SPLIT CIRCUIT may not be totally functional if a component(s) fails.

Why did you get so upset? It was merely a discussion?

[59meteor]

Upset? Hardly, I was simply stating that if the brake pedal goes all the way to the floor, with no resistance, that is sufficient notification, at least to me, and I didn`t need a red brake warning light in the dast to alert me that something was amiss. As for the examples that I gave about brake failures, they were mostly customers vehicles towed in, usually due to a rusted out steel brake line. I did have a couple of similar failures with my personal vehicles, my 85 Mustang split a front rubber flex hose, and my 79 Mercury Zephyr Z7, had the steel brake line , from the firewall to the rear axle. For some reason, Ford elected to run that long brake line under the carpeting, along the right inner rocker panel, so wet carpeting held moisture around the steel line. I also had a couple of brake pedal to the floor failures years ago, with single chamber master cylinder systems, (my 65 Pontiac Tempest had a master cylinder failure, and my 66 Fairlane GTA broke the driveshaft going into high gear at the dragstrip, tearing the factory brake line to the rear axle out, which Ford ran down the transmission tunnel/driveshaft hump). In both the single and dual chamber systems, repeated attempts to pump the brake pedal did nothing other than pump brake fluid out.

[KULTULZ]

Well, I haven't rattled any cages here in a while, so ...

- PROPORTIONING VALVE SELECTION-

Nearly every adjustable proportioning valve on the market today has an adjustable knee point (the point at which the rear brake line pressure begins to be controlled), but a fixed slope (the rate at which it builds beyond the knee point). While one parameter is adjustable, both are critical to system performance.

CENTRIC - https://centricparts.com/getmedia/d9...ing-valves.pdf


The 'SAFETY FEATURE' in a 'DUAL RESERVOIR MC' braking system is not the PDV, but in the design of the MC if it has been maintained correctly and the seals are in good condition.

[Tom S]

I agree 100% with what 59Meteor said. I've got one or two old Ford vehicles, like my plow rig, that never leave the yard & over time one chamber of the dual chambered master cylinders loses all of it's fluid. The brake pedal will go right to the floor & no amount of pumping will restore any braking. Over my many decades I've encountered this on other vehicles several times. In the past I have seen people on this & other boards claim that having a duel master cylinder will allow you to still have brakes on one end of the car if one end loses it's brake fluid but I have yet to see anyone that made that claim say that they actually experienced it to work as they claimed it did.