I have what is probably a simple question but I would just like another opinion. I am replacing all my hard and soft brake lines on my camaro. I have changed to second gen drums when I installed my 9in rear and converted to manual brakes. I am using 83 front calipers(SAE fittings). When it comes to a proportioning valve what are my choices. I was wanting to leave out the original one that mounts by the booster/master cyclinder and just put in one of the adjustable ones in its place (ones with a dial for adjustment). If I went with a aftermarket proportioning valve I would mount it anywhere between the rear port on the master cyclinder and the rear brakes. And just put a "Y" fitting after the forward port on the master cyclinder to branch off to the front brakes. Does this seem correct or am I missing something important. I know this seems like a lot of unnessasary work but the car is comming up from bare bones and it is time for brakes. also if any one knows off hand what the sae thread size is for second gen rear drums and 82-83 front brakes are, that info would be welcome. Thanks, I appriciate any ideas you can offer

I don't like the idea of ditching the factory combination valve on a street driven car.

The combo valve does a few things:
-Proportion valve: Keeps the rear brakes from locking up.
-Hold-off valve: Keeps the front brakes from being applied till the rear brake pressure is enough to overcome the drum brake's return springs.
-Idiot light: Turns on the Brake light on the dash if you have a hydrolic failure. Some people don't even know this and think the brake light is just for the e-brake. I would rather know I didn't have working brakes at all 4 wheels before I rearended someone.

You can still add in a adjustable prop valve with the stock system...or you could replace the stock combo valve with a "T" for the front line, and a 10# residual pressure valve and adjustable prop valve for the rear.

Thanks for the reply. This car will see very little street driving. Mostly to and from the track or a 3-4 mile drive to town for $hits and gigles. I will not miss the idiot light for the few miles it will see. The proportioning will be aftermarket adjustable. But this holding vavle you spoke of I didn't know about. From what I understood of what you said a 10# residual pressure valve will take its place. Only one question, what is a 10# residual pressure vavle and what does it do and where does it go? I am by no means expirienced in building a brake system from scratch so any recomendations are welcome. Thanks again

As far as replacing brake parts, I'd go with a newer model than your '83. All '90-up cars had the same master so I'd install that one, a J50 master.

Ed

The valve will go inline with the rear brake line. 10# valves are used for drum brakes and 2# valves are used on disc brake cars with the MC resovior lower than the calipers (like old hotrods with the MC under the floor).

Here are some links:
http://store.summitracing.com/partde...L%2D260%2D1876
http://store.summitracing.com/partde...L%2D260%2D2220

Thanks for the tips guys. I think I have a pretty good plan now. Going with a second gen MC for maual brakes (Third gen MC's sit at about a 15 degree angle when mounted directly to the firewall, I'd use a S-10 MC but I want to stick with SAE fittings=no bubble flares). Going to rear brakes with an adjustable proportioning valve and 10lb residual pressure valve to the second gen drums on the rear. up front from the MC to line lock to a "T" fitting, out to each stock 83 brake caliper (SAE fittings).

I think I have my bases covered, now to order up some line and fittings. I looked at a company called at www.inlinetube.com and they had most every plumbing parts one would need.

I should be able to get started on this in about a week. I'll let you all know how it turns out when it is done. Again, if I am missing something let me know, brakes are not really something I want to have "almost" right, if you know what I mean.

Thanks again.

but..... the adjustible prop valve allows you to use a more accurate rear brake bias that works for your car.... the factory (esp 3rdgen ones) are set for the far far far margin of saftey. the rear brakes bearly stop at all.... matter of fact, i could probly plug off the rear brakes on alot of 3rdgens and you wouldnt notice the diff.

residual pressure valve takes the place of the hold off valve... AND it gives the added benifit of quicker reaction time in the event of a emergency.


idiot light:
i still dont get it. i mean, before it will come on, you must be pressing the brake already. and for the diff in pressure to be enough that the light comes on, you WILL notice it. it is a usless light that is only there for legal reasons. anyone with half a brain will realize that when the pedal is more then halfway down before the brakes grab, somthing is wrong.
and if they dont....... well i believe in darwin.




lol, anyhoo, heres how you lay it out.... the back port of the master cyl runs the front, and the front port runs the back....

theres a tech article on the main page of the site here: http://www.thirdgen.org/newdesign/tech/propvalve.shtml



heres the basic layout. note that its still two seprate systems like factory.. if one fails the other is there to let you stop.

In my s10 I swapped in manual brake wheel cylinders in order to balance out the brakes with my 12" front brakes (1LE rotors and B-body spindles/calipers). They are 7/8" insted of the normal 3/4". I know the same part will work on G-bodies and I suspect it would work on F-bodies as well. I don't have a problem with the rears not doing their fair share of the work. I am however going to install an adjustable prop valve and disable the factory one.

For a street driven vehicle I like the way the factory hold off system works because both front and rear brakes apply at the same time (or at least close to it). When you have a RPV the front brakes will apply before the rear brakes. Under light braking the rear brakes would never be used.

As for the idiot light I would still like to keep it just because "stuff happens". Mine has come on with my K5 before when my 12bolt drum brakes had a leaky wheel cylinder. With the detached fealing of the brakes on it I can't say I would have noticed the bad wheel cylinder till brake fluid leaked down the tire. The light came on while driving faster than I should have on a windy mtn. road. When the light came on I made a trip around the truck to look for a busted hard/soft line or any major drips. I didn't find any so I topped off the MC and drove home at a slower clip. In my experiance the idiot almost always gives you some warning before you would have felt the difference in the peddle.


For something that isn't driven on the street much and well taken care of obviously none of this matters...

once again I am giving thanks to you guys. Good call on setting me strait on the rear port on the MC going to the front brakes and the front port going to the rear brakes. You all sure do save me alot of headaches! I think this brake setup is going to work out O.K. after all. I ordered up all the tubing and fittings this evening so how ever long that takes to arrive, this part of the project will be underway.

thanks again!

I agree with MrDude_1 on the adjustable proportioning valve. I have one on my 85 IROC and my rear brakes (J65 rear discs) actually work. I "beat the drum" for adjustable proportioning valves any chance I get even though many guys don't seem to think you need them.

One thing to consider though. When you use a factory later model combination/proportioning valve (used on thirdgens) you have to disable the rear brake proportioning valve section. Otherwise your adjustable proportioning valve will be useless.

heh, just be sure you dont link the front and rear sections... you cant "gut" it out...

if you do, when one half fails (say, the rear brake blows a cyl) then all the brakes go out.. not just half.

Hey Blown83. Another nice thing about your brake setup is the fact that you have SAE fittings on your brake line. This makes installing the adjustable prop. valve much easier since you don't have to cut and reflare all the metric bubble flares to the standard double flare to put the new valve in. I'm installing the Wilwood adjustable valve in my 89, which has 1le's up front and pbr discs in the rear. I'm going to pay a shop to mess with cutting and reflaring the lines though, since I have zero experience with flaring brake lines.