residual pressure valve

[LS6 Tommy]

Then why do you need a residual valve when going to a disc/disc MC on a drum brake car?

You don't, unless you remove the proper combination valve, like when you use a full Wilwood or other after market system. Sometimes residual valves are used when the master is level with or lower than the wheel cyliders.

The following info was taken from Power Master Brakes' site:

"There are two different uses for residual valves. The 10 lb valve is used to hold a residual pressure to the drum brakes to keep the shoes out close to the drums giving a higher firmer pedal. The 2 lb valve is used in the disc when the master cylinder is lower than the calipers to prevent back siphoning of the fluid from the master."

Tommy

 

[LS6 Tommy]

Your dealer is sort of wrong. Our cars do no have a proportioning valve. They have a combination valve. The combo valve performs all the duties of a metering valve, proprtioning valve and residual valve. It performs the same job as a residual valve/metering valve by not allowing flow to the front brakes untill a preset pressure is met at the rear drums. It also performs the job of a proportining valve by backing off rear brake pressure as brake pedal pressure is increased to help minimize rear lock up.

Tommy

 

[wiseman79]

This is good info. I've been battling with my brakes since adding the Wilwood master cylinder. I'm still using the stock combo valve, but added the wilwood prop valve between it and the MC. The pedal is ROCK HARD and undrivable. I got this all together this past weekend and have been scratching my head in preparation for another go this weekend. So should I remove the residual valve, is this what's causing the problem? HELP! I prefer having brakes!

 

[355_79bu]

I would get rid of the stock combo valve. Run brake lines to the front with no proportioning valve or residual valve (100% brake pressure straight of the master). Use a t-fitting to split the line to each side of the front brakes. The rear should be run off the master, trough the proportioning valve to the rear brakes, again no residual valve is needed unless your master is below the level of the rear calipers or you are running drums. If you are running a disk/drum setup you will need a metering valve (available aftermarket) hooked in on the front brake lines.

Here are a couple of diagrams for both disk/disk and disk/drum brake systems:

disk/drum: http://ecihotrodbrakes.com/images/pic02_brakefacts.gif

disk/disk: http://ecihotrodbrakes.com/images/pic03_brakefacts.gif

 

[Anonymous]

thanks for the help everybody, looks like i get to spend a little more cash on a afermarket prop valve.