Need help with Prop Valve

[PipsC10]

I have some questions about my brake set up, and how prop valves work. Hopefully someone can school me so I can finish buying my parts. Any help would be greatly appreciated.

My truck was converted to power disc/drum brakes before I purchased it so I have no idea what the set up came from. I do know that the lines from the prop valve to the frame are stock, which I have since replaced with stainless lines.

I would like to purchase a 9 inch dual diaphram booster with master cylinder combo, but all the ones I have seen with the prop valve are different than what was on my truck.

As you can see in the photo of my truck before I ripped it apart, the lines connected to the prop valve from the frame are both exiting from the bottom of the prop valve. All of the photos I have seen of new Prop Valves, one line exits from the bottom, and one from the rear/firewall side. So hear is my questions.......

1. As long as I am using a disc/drum prop valve, does it matter what vehicle it came from?

2. Does anyone know where to find a prop valve like the one in the photo, with both lines exiting at the bottom of the valve?

3. What about adjustable prop valves like the ones Willwood brakes make, can you just replace a stock valve with one of those?

I figured this was a good place to start, and I will probably call CPP or ECE to see if they know also. When it comes to brakes, Im as green as they come. Thanks everyone in advance for any help that can be given........Pip

[PipsC10]

oh and I forgot to mention I tried a search, but it was confusing to me because I know nothing about brakes. Thanks again

[bigblk55]

I don't think the valve pictured is a proportioning valve. It is used in a drum/drum system to turn on the dash light if either the front or back system fails. A prop. valve directs more fluid to the front brakes in a disc/drum system. The disc brakes require more fluid than drums so the bias has to be different so the rear wheels won't lock up before the front.

[PipsC10]

Originally Posted by bigblk55

I don't think the valve pictured is a proportioning valve. It is used in a drum/drum system to turn on the dash light if either the front or back system fails. A prop. valve directs more fluid to the front brakes in a disc/drum system. The disc brakes require more fluid than drums so the bias has to be different so the rear wheels won't lock up before the front.

That would explain why the brakes were horrible and at times my rears would lock up, especially when driving down hill.

[70GMCer]

Definitely not a prop valve in that picture. That is a drum/drum distribution block. Here's the one I took off mine when I went to disk.

[cparman]

Try Master Power Brakes. I bought their 9" booster/master and proportioning valve, and all I had to do is to run a new line from the valve to the brass T just inside the left front wheel. The line size is 3/16, and you will need to use a special fitting that will come with the PROP valve, which will involve double flaring one end of the line going to the front. If you cannot do this get the line about the correct length, and go to your auto repair shop and ask them to do this. we do this for our do it yourselfers. I just rebent the line going to the rear wheels. I will tell you that in a newer/more modern prop valve there are 2 outlets that will go to the front brakes. I used just one of these, and blocked off the other. Works perfect, and looks very clean. I really need to learn how to post pictures. One of those is worth a 1000 words. If you call Master Power Brakes ask to speak to Pat. He is very helpful and will reiterate all of this. Proportioning valves hold a little pressure to the rear drum brakes to help keep the brake pedal full. without this the brake pedal would be low all of the time until you pumped the pedal a couple of time to push the wheel cylinders out.

[Orange]

You have been directed right with all the above posts. I just want to add one thing.
Call Mike at Mike's Bump and Grind Garage...(board vendor)
http://www.bumpandgrindgarage.com/

That's where I bought my prop valve from (disc/drum) and his price is better than any you will find online. Just let him know you came from the board.

DLB

[LONGHAIR]

Proportioning valves hold a little pressure to the rear drum brakes to help keep the brake pedal full. without this the brake pedal would be low all of the time until you pumped the pedal a couple of time to push the wheel cylinders out.

Actually the "residual pressure" valve is in the master cylinder, not the "proportioning valve". That is part of why you need to change masters when making this up-grade.
As stated before, discs reqiure more fluid volume to operate. The correct master cylinder will solve both of these issues.

Your questions:
1) Personally I would use the "correct" one. You need one anyway, why not get the one that belongs there. Power discs were available on these trucks, so there is no "adapting", the right one is available.
2) You don't want one like the photo. Again, get the right one for your truck.
3) Those adjustable units are made to "cut" pressure" to the rear brakes in vehicles that have too much. They go "in-line" after the "factory" style Proportioning valve. You really need the factory one. It serves as the distribution block too.

[Sinisterspeed]

Well this is a thread I might actually be able to help with since I just went through this myself. The proportioning (and residual) valve seen above in the picture. Is just that. For a drum set up it will hold 8lbs pressure in the lines for front and rear. With a disk/drum set up the you need 2lbs residual pressure for the front and 8 for the rear. (if you look at the aftermarket ones one is usually red 8lb while the other is blue 2lb). Then onto the proportioning valve this is all done with one unit from the factory and if you changed to a disk/disk set up you would need to remove it entirely in order to get the correct res. pressure then use the adjustable one to restrict pressure to the rear to prevent lock up. Also the aftermarket ones must be installed before the residual valves.

Since you only went to Disk/Drum this is not necessary. You can you one that came on these trucks 71-72 that had disk front.

I actually have a couple out in the shop right now. You can have for free. You pay to ship it and I will mail it to you.






Hope that Helps

[PipsC10]

thanks to everyone that has responded. All of the information has helped me a lot. I think I am going to order a stock prop valve and bend a new line for the front brakes coming from the valve. Thanks again!

[PipsC10]

Originally Posted by Sinisterspeed

Well this is a thread I might actually be able to help with since I just went through this myself. The proportioning (and residual) valve seen above in the picture. Is just that. For a drum set up it will hold 8lbs pressure in the lines for front and rear. With a disk/drum set up the you need 2lbs residual pressure for the front and 8 for the rear. (if you look at the aftermarket ones one is usually red 8lb while the other is blue 2lb). Then onto the proportioning valve this is all done with one unit from the factory and if you changed to a disk/disk set up you would need to remove it entirely in order to get the correct res. pressure then use the adjustable one to restrict pressure to the rear to prevent lock up. Also the aftermarket ones must be installed before the residual valves.

Since you only went to Disk/Drum this is not necessary. You can you one that came on these trucks 71-72 that had disk front.

I actually have a couple out in the shop right now. You can have for free. You pay to ship it and I will mail it to you.






Hope that Helps

Thanks sinisterspeed for the offer. I am a few months away from finishing my brakes so Im not 100% on how I will finish them off. I also had an offer made to me for a hydroboost set up which would change everything. I will let you know in the future if I need them, again thanks.