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Kwasyd
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Discussion Starter #1
I am installing a brake booster system (pedals, etc) from a early 90's Camaro into my 38' Chevy Sedan. While working with a friend who has built many rods in the past and runs both a 32 Chevy and a 50 Merc, he indicated that he doesn't use proportioning valves in his cars and they are drivers.
He said he has done tests and has seen little value to the valves.
I am wondering what the members of this board feel?
 

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disk/drum................drum/drum................disk/disk?????
Yes...........................no..........................no

Thats with the right master cylinder.
 

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Poncho is alot closer to right than your friend, even with not knowing your system.
If there was no value to them then why do all autos with disc/drum come stock with them?

I would say that whatever your system is composed of, disc, drum or a combination,
Do your own test.
Build your system.
Go somewhere safe and drive fast.
Stand on the brakes.

If the back brakes lock up and the fronts don't,
you need a proportioning valve.

I have seen cars with setups so mismatched that they need one in the front. (T roadster with BIGS and littles)

It all depends on the car, weight distribution, tire size, brake effectiveness.

Later, mikey
 

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In the race cars we run balance bars in order to get the front rear brake bias correct so both ends do equal work..factory does this as well..so tha tis something to look at when doing rod brakes specially when we are mixing and matching brake system pieces..

Sam
 

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Kwasyd
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Discussion Starter #5
Prop Valve

OK, I think that the test is a good idea.
My car has Ford 8" drums on the back and Granada Disks upfront (Mustang II).
I am planning on installing a early/mid 80's booster,pump,pedal set up from a Camaro and then plumbing that into my Ford hardware.
The setup I bought has no Prop Valve, but it sounds like I can add that later if things get ugly during the test.
Thanks again guys.
 

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Are you sure about having 8" drums?


Do you mean an 8" rear with drums?


Given your disc/drum setup, I'd put one in the rear when you initially plumb your system. That way if you need it , all you have to do is turn the knob.

I would feel money ahead if I knew that I didn't have to cut into the lines, flare them, install a valve and then bleed the brake system again.
 

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Kwasyd
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Discussion Starter #7
Proportioning valve

Sorry.. missed the comma.. Ford 8", rear drums..
Thanks for the advice.. I think your point makes sense. Easier to go back then replumb.
 

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Buick Hybrid Guy.
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I take them out on our Turbo Buick's and GMC Typhoon's. We need more line pressure/ballance when you build boost off the line so I remove the Proport. valve and put a T-in. The front brakes are run off the rear of the master and the rear is run off the front.
I don't have any issues with rear or front being more powerfull than one/other.

Hope that helps,
Scott~
 

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Modern proportioning valves are available as adjustable units. This way, you dial in the front/rear bias to your liking, by turning a knob.
 

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Pardon me, guys, for eavesdropping but was curious about something along these lines on my 40 Chevy. I put a MII frontend under it, with 11" discs, 67 Camaro drums on the back. I used a proportional valve with a 10 lb. residual valve in the line going to the rear. Pirate Jack's (where I bought the parts) told me if I had the master cylinder mounted on the firewall, I didn't need a residual valve up front. Cars with the master cylinder under the floor supposedly do need the front residual valve. I'm just building the car and I've only driven it in and out of the shop, but the front brakes seem sensitive. Will installing a residual valve in the front line fix this......or should I wait until I can drive it more?
 

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The residual valve for discs keeps two or three pounds of pressure on the calipers at all times. This is necessary when the M/C/booster is mounted "below" the caliper to keep the caliper from bleeding down into the M/C. Wait until you can drive the car before passing judgement on the front brakes. New pads, new rotors, everything is unbroken in and still sticky.
Mark
 

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Mark, thanks for the tip. What you said about the placement of the M/C is exactly what Pirate Jack's said. I also agree since everything in my system is new, shoes/pads, etc. and nothing has really "seated" yet that I probably shouldn't be too critical of it yet, but just wanted to throw out the question. Thanks again.
Marc
 

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If the fronts seem more sensitive, you may need a metering valve in the front line. This holds pressure from reaching the fronts until the rears start to work, usually 50# . ECI sells them as an individual component, and they are incorporated in all factory disc/drum proportioning valves.

Check it out here

http://ecihotrodbrakes.com/brake_facts.html

Later, mikey
 

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I usually try to plumb in a adjustable value ... like the Wilwood. :D
 

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Here is a photo of a Wilwood adjustable proportioning valve ... installed on my 32 3W coupe. You can also see the 2 lb. and the 10 lb. Wilwood residual valves. I am using a TCI brake pedal kit. I am also using a master cylinder that allows the brake lines to run on the frame side ... not the exhaust side ... :D
 

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Kwasyd
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Discussion Starter #18 (Edited)
Thanks again

for the details. Looks like I have to go back to my friend and have a little chat. He is pretty set in his ways, but I agree. I like the adjustable set up. This way I can your my stock booster set up and then add the prop valve in line.
Thanks all.

One more question ... the residual valves.. are those strictly because of the fact your booster and master sit low in your vehicle?
 

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Most factory disc/ combinations use three types of valves. A metering valve between the front discs and the master cylinder to hold off the discs under light braking conditions until the drums can activate (usually looks like a T fitting). A residual pressure valve to keep slight pressure on the brakes and to prevent air from being sucked into the system when the pedal is suddenly released (usually 2 psi for the front discs and 10 psi for the rear drums). A proportioning valve (sometimes adjustable) in the line to the rear drums to reduce pressure to help prevent rear wheel lock up as the discs need more pressure to operate.

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Any time a master cylinder is below the wheel cylinders or calipers, the fluid has a tendancy to drain back into the master.
This makes for a slightly longer pedal travel upon the first application of brakes after a period of inactivity.

A residual pressure valve is always a good idea with drum brakes, where ever they are in relation to the master, as it keeps some tension on the springs and pressure on the wheel cylinder cup seals..

Many stock drum brake master cylinders have them installed already.

Later, mikey
 
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