Proportioning valve

[Doug&Deb]

I ordered a kit from scarebird for the Coronet. They recommend a proportioning valve. Where should the valve be placed? Close to the mc or close to the rear axle? Or does it matter where? Thanks 

[Adam H P15 D30]

With the stock master cylinder, put the proportioning valve in the rear brake circuit.  I am assuming you are talking about one of these.

[Plymouthy Adams]

2 hours ago, Doug&Deb said:

I ordered a kit from scarebird for the Coronet. They recommend a proportioning valve. Where should the valve be placed? Close to the mc or close to the rear axle? Or does it matter where? Thanks 

 

To me, any company providing updated components/systems for these old car and making recommendation for X parts should have all the facts on their website for the how to and why's...anything less is nothing but a marketing ploy for their main meat and in truth do not really seem to care of the troubles one will have in using their products.  We see this all to often....even with the Pertronix another topic on the forum right now.  They recommend their components throughout the install but do not bother to tell you what may happen and the why it will happen if you deviate.  If they fully explain these things to people I am sure it would boost their sales and eliminate a fair amount of returns under any warranty p[period provided they even warrant the product as misuse is always a disclaimer to void. 

[Plymouthy Adams]

as an aside.  it is just not our cars and the suppliers that try to provide services/parts.   This is across the board for all makes and models.  I sent inquiring of a product listed by a forum for this company and included their actual die numbers for the extrusions for this application in my inquiry...their reply, send us a cross sample.  Well if I was able to get a good cross sample (super deteriorated sample) I can match these up just as well as the next man from folks like Steele and Restoration Specialties listing spec drawing of their examples along with actual dimension.  They even have link for the car maker in their website but nothing listed and they say they have a downloadable catalog but there  is no link on the site.  Right now I am exchanging e-mails asking for the links as the site is not user friendly except to a few pdf for about 50% of the list of cars they say they support. No link for extrusion listings with pictured cross section as the customer service folks states.   While at time the search is part of the fun, often in dealing with companies that fun quickly turns to a degree of frustration.

 

[Doug&Deb]

Thanks Adam. I meant where in the rear circuit. Not sure if position matters or if I should put it where it’s convenient to access. This conversion is new for me. I’d like to do it right the first time. If I make a mistake I may not get a second chance!

[Adam H P15 D30]

Anywhere between the master cylinder and rear axle works.  Have you tried it without the proportioning valve yet?  I didn't need one on my 49 but my 35 Ford needed one, every car is different.

Manufactures have a hard time "standardizing" what components a vehicle may need because of so many variables, they cannot predict brake size, weight bias etc. so it is a mix and match until you have adequate performance.

I have had to reduce master cylinder bore size on every aftermarket master cylinder kits I've installed, power or non power.  Most come with a 1-1/8 master and I've gone down to a small as 7/8.  No kit is a complete bolt in and go.

[Adam H P15 D30]

And to add, my 49 with a stock master, front disc/rear drum didn't need residual pressure valves either.  Even after I removed the factory check valve in the master cylinder.  My 35 needed them front and rear (disc/disc).

[Doug&Deb]

Adam, I haven’t gotten my parts yet. I’m just trying to figure this science project out. I’m going to add a 10lb residual valve and an adjustable proportioning valve in the rear circuit. I’m trying to get the best brakes I can that are a bolt in swap. I don’t have the finances to add a dual circuit mc at this time. I’d rather add some redundancy into the system from the get go instead of waiting for a problem. 

[Adam H P15 D30]

Sounds like you're keeping the stock master cylinder as I did.  Is your rear axle stock or???  I removed the internal check valve from the stock master cylinder and did not install any residual pressure valves or proportioning valve to see how well it functioned.  That was years ago and never had the need to install any other items.  I am running modern 10x2 drum brakes in the rear and a Rusty Hope disc brake kit.

 

Since your stock master cylinder has 2 outlets, consider installing a combination valve if you want added safety.  It wont help if your master cylinder fails but it will help if you blow a line between the valve and the front or rear brakes.  Most come with residual pressure valve built in too.

Edited August 3, 2020 by Adam H P15 D30

[Doug&Deb]

I’ll look into that valve. I’m keeping the stock mc and the stock rear axle and brakes. All hard lines are new nickel copper and the rubber hoses are new. I have two reasons for this conversion. I average 3500 miles a year with my car in sw PA where hills are a way of life. Even my driveway is a hill. I also haul my grandkids a lot so any safety upgrade is a plus. I think I have it figured out on paper, we’ll see how it works. Thanks for the advice.

[Adam H P15 D30]

Seriously though, I would try it with out any added valves and see what happens. Add as needed

[Doug&Deb]

You’re right Adam. The proportioning valve is definitely out. I was overthinking that. I’ll hang onto the residual valve though, it’s just an inline valve and can easily be added later. Just waiting on parts now.

[MarkAubuchon]

On my 47, disc front and 8 3/4 rear end I used a valve for the front (6) and a second (8)for the rear also used a rebuilt stock MC with 7/8 bore.  Stops perfect.  With a stock rear end very important you get the shoes adjusted to spec. good Luck

[Plymouthy Adams]

I agree that the proportioning valve should be an as needed item...the residual valve serves a greater purpose and should be in place.  The removal of the original in the master necessitates that they should be inline.  The difference in pressure rating is also the need for two valves as the master is a single outlet and while 10 is needed to keep just the right amount of pressure on the cylinder cups so not to suck air later, the calipers require less pressure as 10 lbs will cause drag in majority of cases.  Going without residuals have been done but it can easily lead to air in the lines and spongy pedal that will require frequently bleeds to correct.  The original was there for a reason, the later inlines fulfill that need on removal in pressure appropriate for the now newly split system. 

[Sniper]

As an aside, a proportioning valve only handles on part of what you need to combine a disc and drum brake setup.  The combination valve should handle all aspects of making a disc/drum combo play well together. 

 

The combination valve does the following.

 

Proportioning, which the aftermarket proportioning valve will do as well and is the only thing it does.

 

Hold off, which will delay pressure to the discs until a small amount builds in the drums and this only happens once the shoes touch the drum.  This allows both the disc and drums to apply simultaneously keeping one end from locking up or applying with nothing at the other end potentially causing a loss of control.

 

Then there is hinge point, modern self energizing brakes (which most of our stock ones are NOT) are not linear in their application and use leverage to apply the brakes even harder.  Hinge point drops the rate of rear brake pressure increase to keep the rears from locking up in a hard stop. 

 

Finally, there is the pressure differential switch, which is what turns on the BRAKES light telling you that you lost pressure in one of the two circuits.  An attentive drive will probably notice his brakes are not working right, but the average driver needs a warning something is amiss.

 

When I converted my 65 Cuda to disc/drum I used the cop spec Dodge Diplomat braking system, including the factory combination valve.  I figured the factory sorted it well so I'd just copy.  Works very well.  But the problem with combination valves is that they can be very braking system design specific.  I know, for example, that in my cop brake swap there were two possible combination valves used, the difference in the braking system is that one valve was used if it had 10" rear drums, the other for the 11" drums.

[Doug&Deb]

Can anyone tell me what parts come in the scarebird kit. I know I need rotors and calipers. I’d like to order things so I can get moving on this. The kit has shipped, I’m just impatient.

[Plymouthy Adams]

Just now, Doug&Deb said:

Can anyone tell me what parts come in the scarebird kit. I know I need rotors and calipers. I’d like to order things so I can get moving on this. The kit has shipped, I’m just impatient.

 

scarebird can...after all you paid for the kit...it should be on their invoice....folks please learn what you are buying and ensure what you are getting when you buy from these retailers....it is for you own good 

[PT81PlymouthPickup]

Doug&Deb

 

Like Plymouthy, I learned there is a lot of misinformation concerning brake conversions and other products from both retailers and forum members. Also some good information, sometimes a bit difficult to tell which is which. Lots of good opinions that you can pick through and learn from. My advice would be read a lot and be diligent on understanding details before making changes in brake systems. I will say one thing that may raise some eyebrows concerning proportioning valves. Many on here and other forums state their vehicle is just fine without one. Well, from my research that's usually not the case. Proportioning valves are important for panic stops on vehicles with front disc / rear drum setups.. If you get rear brake lockup at higher speeds you could loose control.  Many of these vehicles without a prop valve will stop just fine until that rare emergency panic stop. Knowledgeable street rod builders install adjustable prop. valves in the rear circuit on custom disc / drum to correctly adjust the bias by actually testing it. Car companies use combination valves which are designed and rigorously tested for specific vehicles to set the bias considering  factors such as weight, center of gravity, hydraulic pressure capabilities of components, friction surfaces, etc. For this reason combination valves are usually not used on custom brake systems by professional car builders. Just sayin; Stay safe!

[Doug&Deb]

I appreciate all the advice. At this point the plan is to remove the residual valve from the mc and add a 10lb inline valve in the rear circuit. If I have problems with spongy pedal I’ll add a 2lb valve to the front. One thing I’m curious about. Some have removed only the rubber washer from the residual valve and had success with that. Does that bring the residual pressure down to an acceptable level for the discs to work properly? 

[Plymouthy Adams]

while the disc will work properly..it is the period of time you are not driving that allows the drying of the seal and by pass of air...the slight two pound is there to maintain the every so slight roll of the square o-ring which is your entire pressure seal and the very device that retracts the pistons in the caliper....many misconception on disc brakes out there....the very main thing of the 2lb in this application is that the master is lower than the caliper...the gravity will allow return to the master and lessen the chance of the o-ring staying fully wet and thus not sealing.  This in our application with the lower master is the better argument for the 2lb residual...some do not use it and have had luck...I would say that luck is directly proportional to the frequency of use of the vehicle.   Over time and parked condition the odds of sucking air increases... 

Edited August 6, 2020 by Plymouthy Adams

[Doug&Deb]

Good advice Mr. Adams. Since I’m already adding one inline valve another one for the front sounds like cheap insurance. 

[Adam H P15 D30]

@Doug&Deb I just removed the rubber check valve and reinstalled the "cage" it sat in.  Did this while it was on the car.

My 49: 7 years ago I added disc brakes, replaced the rear axle (modern drum system), removed this valve and added no other valves.  When I was testing it, the rear brakes would lock up just before the front brakes.  With performance like that I saw no need to add anything further.  I've let this car sit for 6 months at a time and the brake pedal is right at the top when I go to move it.  Once again, no reason to add anything to a properly performing brake system light years ahead of the original drum/drum system.  Never a leak or issue during this time.

My 35: disc/disc/power/dual MC started getting a low pedal sitting for a couple of weeks, I added 2lb residual pressure valves to solve this.  Rear brakes locked way before the fronts, I added an adjustable proportioning valve.  Works as well as my Dodge now.

47 Ford:  Disc/drum, non power dual master cylinder with CPP combination valve.  YES, most aftermarket brake companies offer and recommend a combination valve in custom brake systems to take advantage of its many benefits.  You can still add an adjustable proportioning valve if needed.  The 47 Ford has this combination valve and out performs both the 49 and 35 in braking but not by a large margin.

Point is, there is no "one system fits all" and you must have component X or Y or it won't work correctly and kill you and everyone around you.  Reason I stated earlier to try it without and TEST it because you might find you don't need all that extra stuff after all.

[PT81PlymouthPickup]

41 minutes ago, Adam H P15 D30 said:

@Doug&Deb I just removed the rubber check valve and reinstalled the "cage" it sat in.  Did this while it was on the car.

My 49: 7 years ago I added disc brakes, replaced the rear axle (modern drum system), removed this valve and added no other valves.  When I was testing it, the rear brakes would lock up just before the front brakes.  With performance like that I saw no need to add anything further.  I've let this car sit for 6 months at a time and the brake pedal is right at the top when I go to move it.  Once again, no reason to add anything to a properly performing brake system light years ahead of the original drum/drum system.  Never a leak or issue during this time.

My 35: disc/disc/power/dual MC started getting a low pedal sitting for a couple of weeks, I added 2lb residual pressure valves to solve this.  Rear brakes locked way before the fronts, I added an adjustable proportioning valve.  Works as well as my Dodge now.

47 Ford:  Disc/drum, non power dual master cylinder with CPP combination valve.  YES, most aftermarket brake companies offer and recommend a combination valve in custom brake systems to take advantage of its many benefits.  You can still add an adjustable proportioning valve if needed.  The 47 Ford has this combination valve and out performs both the 49 and 35 in braking but not by a large margin.

Point is, there is no "one system fits all" and you must have component X or Y or it won't work correctly and kill you and everyone around you.  Reason I stated earlier to try it without and TEST it because you might find you don't need all that extra stuff after all.

I agree! There were some disc / drum vehicles from the factory that did not have proportioning valves, although only a few. My worry, is that vintage auto brake systems often get tampered with by amateur mechanics and are supposedly upgraded with kits and mismatched components and sometimes will seem OK for the most part, Until a panic stop! I'm just being a voice of reason and suggest that anyone making changes to braking systems to really test them thoroughly hard somewhere you won't hurt or kill anyone before thinking you're good to go. I'm an advocate of split masters as well. I once slammed on my original brakes when a deer jumped in my path. The master cylinder failed (No brakes at all) and I almost flipped my old truck narrowly missing a head on collision. She now has a disc / drum, 2lb residual frt, 10lb residual rear, adjustable prop. valve which was needed to get the bias correct. The brakes seemed fine until I really pushed the limits.

[MackTheFinger]

I just installed a duel reservoir master cylinder on the firewall on my "rescue dog" '47 D24. (See classifieds) The only original m/cyl I have is rusted shut and there were some good dual reservoir m/cyls with the car. The clutch pedal will still have to go through the floor but that doesn't seem like a big deal. As long as you're digging that deep into your braking system you should give it some consideration. 

[Doug&Deb]

I understand the concerns about tampering with the brake system. I’m simply trying to improve the brakes without re-engineering everything. Everything I’m doing is a bolt on swap. It can easily be put back to stock. Anything I do has to be better than perpetually mis- adjusted brakes. My front drums were at the limit when I last had them turned. I don’t have the correct tool to adjust the brakes and my homemade tool is marginal at best. I’m going to see how this works and hopefully not kill my self in the process. I’ll keep everyone posted.