Rear proportioning valve questions/pics

[JimR.]

Hello folks.  I do not own a Camaro, used to (68 SS 'vert, wish I stil had ).  I own a '70 Chevelle SS now and was sent over to this group for some help/clarification from the folks on the Team Chevelle site.  I did a lot of searching/reading through your posts and had a few back forth e-mails with John Hinckley. I am very grateful for his time and assistance.  (Man is he a mountain of information!) Here is my issue.  Was redoing the brake lines on my Chevelle.  Factory disc/drum setup.  Had a bad front hold-off valve and a leaky MC.  Figured while I was at it, i would replace the rear prop valve as well since it was 39 years old along with some new brake lines.  I bought the front hold -off valve and the new rear prop from Inline Tube.  Could not get any fluid past the rear valve to bleed the brakes.  I can't even blow air through it with a compressor.  John agrees that the new valve is defective.  The first 2 photos below are courtesy of your site here.  The 3rd one is my original prop valve on my Chevelle.  Last is the new rear prop I purchased.  If I understand this correctly, the inlet side of this valve I have marked with a red arrow.  It is the top fitting which if I imagine the internals, would be above the spring so it can push down on it and get flow through the valve.  Outlet is the blue fitting.  OK, that makes sense in my head.  This is on your Camaro though.  On my Chevelle, it uses a valve that looks the same, but with different mounting bracket configuration.  The inlet is the lower/mid valve fitting and the outlet is the top one.  As if you were to take your valve, disconnect it, flip it around and re-install.  How the heck would it ever flow anything??   I can only guess that the internals are different for a Chevelle prop valve that a Camaro valve?  I can't seem to figure out how my original one ever worked unless the guts are different.  Does anybody here have any ideas? 
John's valve


Internals


my 39 year old cruddy original valve


The valve I purchased, looks identical to my old one, but does not flow


Here is the car.  Thank goodness it isn't as ugly on top as it is underside.  I want to drive it but it has no brakes!!!  HELP

[Grsmnkey]

Hi,

On my 68 if you look at your first picture (john's) the side you have marked outlet, is my inlet (i.e. it is attached to the master cylinder).  The side you have marked inlet is my outlet (i.e. it is attached to the brake line going to the rear axle).  The big bolt's head is on the bottom parallel to the ground.

Examining John's picture I believe that is the case as well. What leads me to this conclusion...At the top of the picture it looks like the floor pan plug, the large bolts head must be parallel to the ground, and it must be on the left (drivers) side of the sub frame.

Anyway that's how mine is mounted, hope that helps 

[JohnZ]

Jim, in the photo of my valve above, the fitting on the left is the inlet, and the fitting on the right is the outlet - I think the "R" stamped on the valve adjacent to the fitting on the right stands for "rear".

[JohnKY]

I think what may be confusing you is this: The Camaro valve is mounted on the outside of the frame rail. The Chevelle valve is on the inside of the frame rail, thus making the inlet and outlet lines appear reversed.

[JimR]

I think what may be confusing you is this: The Camaro valve is mounted on the outside of the frame rail. The Chevelle valve is on the inside of the frame rail, thus making the inlet and outlet lines appear reversed.

Bingo!  Yes, i did not realize that.  So the inlet/outlets are the same as my valve on my car.  Ok, then I have no idea how the valve works internally.  Gonna have to open my old one up and see if I can get it apart without ruining it.  Thanks for the replies/help guys.  I really appreciate it.  

[JimR.]

Update,
Got the replacement valve and I was able to blow air through it.  Took it apart and it looks the same as my old one except different color piston and slightly different spring.  I rigged up a test fixture in my garage to give it up to 1500 psi inlet pressure in 100 psi increments.  The old valve showed the same pressure out as it did in, so I guess it was just leaking through constantly.  Ie; 200 in = 200 out, 600 in = 600 out and 1500 in =about 1350 out.
The new valve showed 1500 psi in and 800 psi out.  So at least it looks like a proportioning valve.  I got shipped out of town for business, so I have not yet had time to install and bleed brakes, but I am optimistic this time.  Thanks to all on this site for your help sharing the knowledge.  Pics below of valve comparison and testing of the old valve.....

[KurtS]

There's an old Service News that tells what the in/out pressures are supposed to be. It's a 1970 or so issue.

[JohnZ]

There's an old Service News that tells what the in/out pressures are supposed to be. It's a 1970 or so issue.

Kurt - I sent that info to Jim:

GM/Kelsey-Hayes specs for the limiting curve in the valve are as follows, with input psi followed by output psi:
 
0    0
200    200
270    230-270
400    290-335
600    375-420
800    455-510
1000    535-600
1500    735-825
2000    935-1025

[JimR.]

Yep, John had sent me that info in a prior communication.  So looks like the new valve at 1500 in/ 800 out is pretty good.
Thanks all.