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Old 10-12-2007, 10:47 AM
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Do i need Proportioning Valves...?

i put a 79 Cutlass rear end (drums) on my 51 Buick. i am using the stock 51 master cylinder and front drums. i noticed that after driving it for a while and using the brakes, the pedal gets very very stiff! to the point that the brakes are slightly engaged. i know they are engaged because if i put the car in Neutral while rolling it soon comes to a stop.

so, do i need proportioning valves? if so, how does that work.

Thanks,
Yaril

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Old 10-12-2007, 11:06 AM
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Wow, I'm going to be a little rough on ya here. Your lack of brake knowledge is scary. Please learn about brakes before doing anything else. I wonder what else is wrong that you haven't discovered yet.
There is a lot of information out there for free...

To address your question, maybe...

A proportioning valve will not solve your problem, it's use is to change the amount of fluid pressure getting to the rear brakes to balance the car. You might need the valve, but it won't fix this issue.

Your problem is either a mis adjusted brake pedal push rod or bad brakes or bad lines or something else maybe
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Old 10-12-2007, 11:11 AM
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Agreed. You can't just put something in and expect it to be a match. Brakes are very delicately balanced things, volumes, pressures, flows, mechanical advantage, leverage, surface area, coefficient of friction. You can't just put brakes together and expect them to work... especially when you're putting brakes originally designed for power assist in a car that doesn't have it.

I suggest taking it off the road until you can design a complete system that will work. Otherwise you risk killing yourself and others (literally).
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Old 10-12-2007, 11:25 AM
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i was afraid id get this kind of response. guess ill start by adjusting the bands. the front cylinders are both new the shoes are in good shape and the master was also rebuilt.

i don't remember if that cutlass had power brakes (probably did). i had the drums resurfaced and the shoes looked good.

so if the cutlass had power brakes... how can i calculate or know what valve to use?

thanks for the speedy replies!
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Old 10-12-2007, 12:04 PM
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Your main problem is the master cylinder. Replace it with one that is the correct size for the brakes you're using. Also replace the stock front brakes with something a bit more modern so everything will work together. Also, don't forget to bench bleed the new master cylinder before you install it.
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Old 10-12-2007, 02:03 PM
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No need to beat you up but brakes are important, when I was 16 I put a caddy rear under my 55 chevy and had no clue what I was doing!
Your problem as pointed out is not a proportioning valve, drum brake systems have what are called residual valves and they come in different values, 2lb, 5lb 10lb etc. Drum barkes have return springs to pull the shoes away from drums when the brakes are released, the residual valve holds a small amount of pressure in the brake lines so the wheel cylinders don't collapse completely when the brake is released, if they did as the brake shoes wore you would use all your pedal travel just pumping up the wheelk cylinders.
Master power Brakes (www.mpbrakes.com ) has an excellent web site with good technical information. I think your residual valve is too strong, or maybe you now have two in the system and it's not letting the wheel cylinders release. Check out the web site, research what residual valve came with the car and what's required for your rearend and I think you will find your answer.
Good Luck!
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Old 10-12-2007, 04:00 PM
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If he replaces his master cylinder with one that is made for a modern drum/drum system it should have the proper residual valve built in.
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Old 10-12-2007, 04:38 PM
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A good start is to at least match up the master cylinder with the brake cylinders. Go to a parts store and ask to see their brake parts catalog. What you'll have to do is look up all the part numbers for the old car and the "new" car's brake parts. Then go to the back of the catalog where it lists master cylinder bore and stroke as well as wheel cylinder bore. You need to keep the same proportions as you had before. If you had a 3/4" front and 7/8" rear master cylinder along with 3/4" wheel cylinders at all four corners, you can't just swap in an axle that has 1" wheel cylinders or it will get too much pressure and not enough volume.

Aftermarket brake companies have already done this homework for you, so I suggest a kit if one is made.
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Old 10-23-2007, 10:06 AM
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well, i think the brakes are fixed. it was way simpler than all that stuff. it seems that the brake pedal was not fully retracting (it was hitting a removable floor section) so i tried to adjust the brake rod (no luck its stuck), so i grooved the removable floor so the pedal doesnt hit it. i drove the car and the brakes work. so far so good. thanks.
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Old 10-23-2007, 11:26 AM
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MAN!...... I WISH FL would bring back vehicle inspections....to eliminate some of this "accidents waiting to happen BS"

tyler,
plenty of oem cars articles online (motor trend etc) that will tell you what your 60mph to 0mph stopping distance footage needs to be based on your car wt and wt distribution....
find some data and test your car!
before you kill some kid on a bicycle!

let me guess, the 51' master cylinder you are using is a single port master....
you do understand that means that if ANY hydraulic part fails (hose/wheel cylinder/steel line/etc)....you instantly have NO BRAKES AT ALL!

(as Centerline and others posted)
GO GET A DUAL PORT MASTER ($60? for a rebuilt) THAT MATCHES YOUR WHEEL CYINDERS!!!!
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Old 10-23-2007, 12:08 PM
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red65mustang, i understand your concern, that is why i posted this thread. nobody until now (you) have told me to go get a dual port master. i know the advantages of those because i have one in my other car. thank you.
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Old 10-24-2007, 09:43 AM
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Power Steering for my 53 Pontiac Chieftain

Not so fast sparky. Do you have a frame mounted master cylinder, or firewall mount? Frame mount is not a simple swap. Even with a firewall mount, don't leap till you look. It's a PITA, but you really need to follow the advice here and learn everything you can about your brakes system. Understand volume and pressure and the effect mismatched components have on each. If your new MC is too big, you won't have the leg power to push it, without a booster. If it's too small, you won't have enough fluid in the system. Save money and frustration by learning and planning, before you spend a dime or tun a wrench. been there, done that.
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Old 10-24-2007, 10:01 AM
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thanks oldguy, trust me i was not planning to just order stuff. i am already on Buick forums finding out what others have done. my M/C is chassis mounted and i would like to keep it as stock looking as possible, no power brakes. i'm sorry but i do not like the look of that buster in my engine bay. i do understand the importance of the braking system and the advantage of the dual m/c. to be honest i drove this car (stock mechanicals) for nearly 4 years and never had a problem, but if i can upgrade while maintaining the same look then im ok with it.

thanks.

ps, the brakes are working fine, now that the pedal can fully retract the pressure isn't building up. it brakes consistently the same.
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Old 10-24-2007, 11:12 AM
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do I need prop valve

great, good luck. don't be afraid to think outside the box. The MC can be mounted behind the pedals pointing the opposite direction, if there is more room there to get a booster in. Just takes some mods on the linkage.
You might also enjoy this wiki http://www.crankshaftcoalition.com/w...ension_upgrade

There are some tips in there to upgrade while keeping drum brakes.
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