Residual Valves

[McDenny]

I figured I would use a proportioning valve so I could adjust the brakes from front to rear. I know you would adjust the pressure if you were running disc and drums on the same car, but also so the front doesn't over brake compared to the rear, if using disc all the way around.

 

[Ma_n_Pa T]

OK, I have a question....how do I tell if the master has residual valves in it? I am going to use a Wilwood proportioning valve and I am going to run disc brakes all the way around too, I was not going to use residual valves until I read this and now I am second guessing myself. I have heard stories about them not releasing the pressure in calipers and making the brakes get hot. But like it was mentioned before, I don't want to run all my brake lines then figure out I need them.

Before '68, the residual pressure valve was in the master cylinder bore. After '68, RPVs were typically placed at the exit ports, just behind the inverted flare. where they arc easily removed with a sheet metal screw. In fact some are threaded— some kits include a screw if you are using the master on a disc/disc system (remove both). The internal components in the masters listed are the same and can be used for both applications by simply removing the residual check valve for the disc end of your car, or remove both valves for disc/disc applications, and leave the check valves if you have four wheel drum brakes (check photos).
How do you check for the existence of an RPV'? Just remove the inverted seat so you can see the exit port Behind the brass inverted flare is a black (round base) rubber "duck bill" that goes up into the back of the brass inverted flare. This is the residual check valve. It is held behind the inverted flare with a small spring. Remove the spring and "duck bill" for disc brake setups and leave it in for drum brakes If your system is split drum/disc only remove one Do not forget and leave out the brass inverted flare, since this is what seats the double flare on the brake line itself. (copied from a brake artical)

Drum brakes have return springs and they at one time was returning too fast and blowing out the seals in the slaves because of the seal design, they have since fixed the problem, if you are running an old axle and think you have one of the old slaves replace it with a new one, dam cheep 15 dollor fix for good brakes.

As for in line RPV's I do not run any in my system, I have drums on the rear and GM Metric disc on the front, been working fine since 2006, I have a problem with people thinking fluid will feed back into the master when there is no leak in the line, calipers do not have return springs, drums do but the piston returns all the way as soon as you release the brake, it is a sealed system. If it drains the fluid back to the master you best start looking for a leak or start replacing the master or slaves.
Always buy new parts when it comes to brakes.

Just my thoughts,
Jerry

 

[RESINATOR]

Ma n Pa covered this very well. One other thing to consider is the type of Calipers being used. An OEM style Caliper (Ford or Chevy) may not have a return spring but they do retract differently than a Wilwood style Caliper, so to keep the pads from "Rattling" when no pedal pressure is being applied, a 2lb Residual valve would be recommended.
The issue about running a Proportioning valve has to do with balance front to rear, a proportioning valve only reduces pressure to the line it is installed into. So if you had the same Calipers front and rear, plus the same rotor diameters, you should be relatively balanced, but lets say you have a tiny front wheel and a massive rear wheel. You may need to compensate for that, so a proportioning valve may need to be put in the front line to cut the pressure down to balance the system. Same thing for lets say a 175 H/A or Wilwood caliper, you would not want that caliper running at full pressure so you would almost always run a proportioning valve in that line so you can adjust the amount of braking it will do.(The 150 and 175 calipers do not use a residual valve because of thier design)

Jerry

 

[Zack]

thanks for clearing this up guys.

 

[McDenny]

Thank you for all the feedback, I appreciate it.

 

[Track T-4]

Great info on this thread...my winter project. Thanks.