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Discussion Starter · #1 ·
i put power disc brakes on my 69 camaro, the front is a new standard disc kit and the rear is off a 1979 tran am ws6 car, the booster and master cylinder is also new.

i bled the front and get some fluid pressure but not a lot, enough to grab if the pedal is to the floor, but can only get a trickle of fluid to the back.( not enough to move the calipers).

my question is can i use the stock proportioning valve that was on my car or do i need to change it or what else could be the problem?


thanks for any help.
 

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Assuming booster/pedal/pushrod linkage is all correct...
Try bleeding the rear port of the master cylinder at the fitting while it's on the car. Most times it will have air in it and make bleeding the rear brakes difficult or impossible. This must be done even if bench bled. I always do the front one too.
Once you know you have a good fluid stream at that fitting you should have a little better pedal, but you might have to get the air bubble out of the rear line before it's firm, which might take a little while.

Stock 5 port valve has no proportioner. It just distributes fluid and trips the dash light. Same for all brake systems on the 67-69.
Stock disc/drum rear brake proportioner (under driver on frame, if equipped) is set up for a different system and should be replaced with an adjustable type for your 4wldisc. Stock disc/drum front brake hold-off valve (next to master, in front line) is unecessary and undesireable with 4wldisc.
 

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I bled my 71 formula with the same set up forever. I replaced the prop valve, and master, with no luck.
I finally got a good, (not great) pedal after adjusting the e brake lever, on the caliper. It's been a long time...20 years, but take the lever off, reinstall the lever nut on the stud. I believe I had some needle nose vice grips on the flat part of the stud,between the lever nut and caliper. Keep the grips tight to the caliper.. there is a seal, or something that will come out if not tight.Using the vice grips and a wrench in the stud I was able to adjust up the parking brake. Trick is to adjust it just right so the lever will go back on and have the pad/rotor clearence right.
After that, brakes were good.
I rered what I wrote above, and I the vice grip part makes no sense, maybe they were not locked on the stud. Maybe I used them to just keep the seal in the caliper. I would have to see the caliper again to know.
I know it makes no sense, but dont take the process literally, look at the lever, and what it does, you will figure it out.
 

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When I had a problem with the rear it was a colapsed rea flex hose. I replaced the hose and problem solved.
 

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I have the same setup on my 69.The problem is probably the e-brake like Dale said.It has to be adjusted correctly for the hydraulics to work.Given the amount of grief this setup caused me to get working (and I'm still not convinced it's working properly) I think an aftermarket kit would have probably been more cost-effective. If you get it working make sure you use the e-brake whenever you park the car.Those calipers rely on the e-brake to self-adjust.
 

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I've got the same rear brakes on my Firebird, but don't have any issues with it, brakes work really well. I did use the prop. valve off of the T/A, though. I don't know if you want to run a prop. valve designed for rear drums, which, by design, are self-energizing. Discs, by design, are not self-energizing, and need a lot of fluid to work properly. After adjusting the calipers so that both work properly with e-brake on, and it still doesn't feel right, change the prop. valve with one designed for 4 wheel discs.
 

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Discussion Starter · #8 ·
thanks guys for the help, i am going to try some of your ideas this week.

fyi. i do not have the valve under the drivers side of the car just the one under the master cylinder and i think it is a drum to drum prop. valve.
i have bled the master to prop valve (good pressure) and from prope valve to rear lines(not so good pressure).

so I need a disc/disc prop valve and ajusted the rear calipers right?
let me know .

thanks!
 

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The standard block on a drum/drum system is just for fluid distribution and someplace to screw the brake light switch.

There is no hydraulic valving in it at all.

It's perfectly OK to continue to use this block with a disk / drum or disk / disk setup, all it does is split the front hydraulics for 2 lines and light the light.

You'd need a proportioning valve if the rear brakes lock before the fronts. A disk / drum setup will always need one, cause the back drum brakes don't need anywhere near as much pressure as the front disks. A properly sized disk / disk setup normally won't need one. If the rears lock first, get one that is adjustable.
 
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