spode134

I have a 79 that i am installing an adjustable rear brake proportioning valve in. I have bought a new master[79] and am not sure of the outlets to use on the master. According to the manual the rear circuit uses diagonal division and a separate regulator for each wheel. I need one line to go into the adj. reg for the rear which will then tee into the two lines, one for each wheel.Which port should I use and is only one ok? As for the front it will come straight out of the master but from which outlets?
I am using a caliper set-up from a 89 with the 79 master and 10" booster.

Darrin.
85 5 speed street
79 5 speed caged, leda suspension,
engine going in soon.

GlenL

This is difficult as you're looking to re-work the basic operation of the system.

Your car has a diagonal split where the rear-most chamber (towards booster) in the master pressurizes the right-front and left-rear brakes. The forwards chamber booster pressurizes the left-front and right-rear. This is why there are two pressure regulators.

The two chamber in the master give the same pressure. With one regulator I'd suggest running both front brakes off the forward chamber and both rear brakes off the rear chamber. There are two outlets on each so you'd need to plug one on the rear. The remaining outlet would go to the regulator and there would need to be a "Y" to connect both rear brakes.

Might be easier to get two regulators...

Jim bailey - 928 International

the diagonal has right front and left rear on the same piston, left front right rear same piston of the master. The later cars S-4 have two different size pistons in the master the larger drives the two big front calipers the smaller front piston the rear calipers through a single proportioning valve. You probably should use the S-4 master and replumb your brake lines. Be careful with your current setup or you might have three calipers on one piston and only one on the other and that would be a BAD THING..

spode134

Update on the master cylinder... looking at one that is apart . There are two chambers in the master cylinder, sepatated by lip seals. The ports at the back are one chamber the ones at the front the other. But the piston for the back is pushed on directly by the pedal. The piston for the front has a compression spring in between it and the rear portion of the piston. Both the same size and volume so... I figure put the front calipers to the direct chamber[rear ports] and the rear calipers to the front chamber. I'm guessing that at some point of hydraulic resistance the chamber with the spring pushing on it will limit out as to how much pressure so that should be the rears being fed through the proprtioning valve.

DoubleNutz

I used adjustable brake vavle proportioning in my 85S (PRDATR). Easy install, I put the adjustment valve in the rear spare tire area (since I did not carry a spare). Among the best things I ever did to set up my break proportioning for the street and the the track. Just dont forget to turn down that rear higher bias when driving on the street... if you get caught in the rain with that cranked up it could be disasterous.

GlenL

When the system is bled the chambers produce the same pressure. If the rear chamber is full the spring won't compress at all. The spring is there to make sure both chambers have equal presure.

Note that DNutz has the later brake system that Jim was describing. In that case one chamber feeds both rears and one line Ys at the rear to feed both brakes.