Proportioning valve / rear brake problems

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cooooledart

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I just installed the wilwood front disc brake kit on my 69 dart, the backs are still drums. I have the proportioning valve and the residual pressure valve installed, does it matter what order they are in? With the proportioning valve set so that the fronts get the most juice, the back left will still lock up first. The back right does not lock up and niether do the front, only the back left. Any ideas? I also have a new m.c. from wilwood, which we did bench bleed first.
 
On the position of the residual pressure valve I would guess it needs to be as close to the m/c as possible. I would contact wilwood to be sure if there are no instructions. As far as left rear locking and no others, my thoughts are brake shoe adjustment, contaminated brake shoes or different bore size wheels cylinders, possibly primary and secondary brake shoes in wrong positions. Just my thoughts.
 
Is there a chance that the P-valve is plumbed backwards?

You may have 2 issues.
It seems like the front brakes are not working,or not working right; and there is definitely a problem in the rear.As to the rears, only one side is working, the side that is locking up.
If it was me I would isolate the systems and work on one end at a time.

Yes the R-valve ought to be closer to the M/C than the P-valve. However, I don't think it's a big deal. It's job is just to keep a little pressure in the rear wheel cylinders to keep the rubber cups tight against the cylinder walls.This tends to keep leakage to a minimum, back there.
 
cooooledart said:
... With the proportioning valve set so that the fronts get the most juice ...
Click to expand...
Makes me wonder a bit. Post a photo. An adjustable proportioning valve has a single inlet and outlet and is plumbed only in the rear tubing. If your front tubes go to it, it is a "combination valve" and much more complicated. The proportioning valve decreases pressure to the rears, so no way you could adjust it other than your statement. Regardless, both rear wheel cylinders should see the same pressure, so the left locking up and not the right is likely one of the stated hypothesis (gunk on shoes, wrong shoe assembly, adjustment, ...).

I understand that the only people who require a residual valve today are hot rodders who install the MC below the floor. Otherwise, the "new design" wheel cylinders (meaning ~1970+ or so) have cups on the spring ends (or tight coils) that keep the rubber seals tight. But, doesn't hurt to use one if you plumb it correctly (usually right at MC port).
 
klingon said:
How did it all fit just got the kit to
Click to expand...

Now that its all done, it fit well. but during the actual process of putting it together, I wish i would've gone with a more common disc brake kit, that way I couldve gotten more help with people on this site. If I were in your position, I would do a lot of research on this sight and see what everyone else is running.
 
It appears to me that you have plumbed it in reverse. The chamber closest to the firewall should be plumbed to the front brake system. If I am correct about the reversal, you need to correct this.The rearmost part of the valve inside the master is directly coupled to the brake pedal, whereas the part that is designed to activate the rear brakes( which is the forwardmost chamber) is hydraulically coupled. It may be confusing, but the rear chamber is the front, and the front chamber is the rear.
Your brakes will work either way it is plumbed on the inlet side of the P valve. But if you have a failure in one end of the system, that's when the problem arises.You really want the front brakes directly coupled to the pedal.The fronts do 70 to 85 percent of the work, on most cars. The rear usually fails first.
Depending on what's going on on the outlet side of your P-valve, you may be proportioning the front brakes. The ports on the valve are coded. You will see FI,RI,FO,and RO. F is front, R is Rear, I is Inlet and O is outlet.If you cannot see the coding; the switch-end is for the front brakes. The topside are inlets, and the bottomside are outlets. The knobside is the top.
 
Just food for thought, I used the wilwood master and Wilwood 4 wheel discs. First the front, then added the rear when I upgraded to a dana. Never changed the prop valve or anything, works fine.
 
So you only need a residual valve if your master cylinder is below the horizon plane of the disk brake calipers (street rods). Sounds like you have it plumbed wrong. You also my not need much on the proportioning valve. I didn't even need it with 9 inch brakes in the rear still.
 
Since the R-valve is already plumbed, (correctly I assume;they are directional), I would leave it where it is. There's no telling what might,or what might not,currently be in the old rear wheel cylinders. Doubling up is ok.
Yes it's very possible to not need a P-valve with 9"brakes out back, and discs up front. It's also possible to not need one with 10"rear brakes and 295s. Lot's of things are possible. But the OP already has a P-valve installed. It may just be a matter of swapping two lines to get it functioning properly.
Why make him redo all his plumbing to satisfy a possibility. And his P-valve appears to actually be a C-valve, which turns the dash lite on in the event of a pressure differential across it. Here in MB the dash lite has to be functioning properly,so he would be required to plumb a safety valve in there instead. Why make more trouble for him than he already has? And since I am licensed to perform safeties here in MB, the brake system is one area I scrutinize.
 
did you get it figured out? i have the exact same set up that im ready to install and any advice would be great
 
AJ's observations that the F and R ports from the MC were reversed is correct. In the pix above, the rear port form the MC should go to the top front port on the combo valve, and the front port on the MC should go to the top rear port on the combo valve. Here is the Wilwood link that has the info:
http://www.wilwood.com/MasterCylinders/MasterCylinderValves.aspx
Go to this link and see the 2nd part down the page, and follow the link to the 'Proportioning Valve Drawing'.

And yes, this is a 'combo' valve, with both an adjustable proportioning section (the knob) and a system failure switch (the electrical connection).
 
I fixed the problem a while ago, it had nothing to do with the master cylinder but with the rear drums themselves. Works fine now
 
Good result. Many here claim, "drums don't work". But, commonly they never give them a chance like replace parts correctly. On my 1964, new shoes were installed all wrong w/ 2 long linings on one side and 2 short linings on the other. That does make the brakes pull to one side.
 
cooooledart said:
I fixed the problem a while ago, it had nothing to do with the master cylinder but with the rear drums themselves. Works fine now
Click to expand...

Thanks for the update... Although it kinda sucks that problems are posted but need to be coerced for an answer if it was solved or not.. Common forum issues. It doesn't help anyone else who is spending hours and hours searching for an answer solve the problem.
 
The star wheels were on backwards and not engaging, causing the drums to lock up every time. More surprises from the previous owner
 
Mine use to lock up too, I went with smaller slave cylinders on the rears which helped some but didn't completely solve the problem. I then took the shoes off and ground the ends so they didn't grab so much... solved the problem.
 
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