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I have a GM style Prop Valve from Right Stuff.

#2 Well - I will try that. All I gota do is start the car and let the fluid circulate. Everything is Ready to go. I don't understand it - But wont hurt to try it
There's a little more to it than that. Look for some bleeding instructions.
 

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Discussion Starter · #62 ·
There's a little more to it than that. Look for some bleeding instructions.
I will call POL and ask them - I do have the Paperwork they sent me. I will read threw it also
 

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I had one for a GM truck with large rear drums, and large single calipers up front. That proportion valve looked the same as the one off of the Rivera with 4 wheel disk. They looked the same, but didn't work the same. The 4 wheel disk valve was obviously different in the valving or spring pressure. Just something to think about. When parts are mismatched sometimes it's hard to diagnose where it's going wrong. I'm running a factory single piston caliper set up on the front , and an 11" drum set up on the rear with a factory booster, and DOT 5 fluid. It will never stop like an ABS newer car, but it stops great, with no pedal fade or sponginess. I hope you figure it out soon.
 
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Discussion Starter · #64 ·
I had one for a GM truck with large rear drums, and large single calipers up front. That proportion valve looked the same as the one off of the Rivera with 4 wheel disk. They looked the same, but didn't work the same. The 4 wheel disk valve was obviously different in the valving or spring pressure. Just something to think about. When parts are mismatched sometimes it's hard to diagnose where it's going wrong. I'm running a factory single piston caliper set up on the front , and an 11" drum set up on the rear with a factory booster, and DOT 5 fluid. It will never stop like an ABS newer car, but it stops great, with no pedal fade or sponginess. I hope you figure it out soon.
I Checked. Its a Right Stuff Prop Valve. Its a disk up front and disk in rear Prop Valve. I have had Extensive conversations about this prop valve with a few of the wilwood guys. Its Not off a Rivey but its it ment for Disk front and back
 

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Chuck that prop valve in the trash and get an adjustable one. Wilwood has a couple of options. Some 2 psi residual pressure valves might help too.

Maybe while you’re at it toss those metric cadillac calipers in the trash too. Less braking force than stock drum brakes…

Don
 
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Discussion Starter · #66 ·
Chuck that prop valve in the trash and get an adjustable one. Wilwood has a couple of options. Some 2 psi residual pressure valves might help too.

Maybe while you’re at it toss those metric cadillac calipers in the trash too. Less braking force than stock drum brakes…

Don
I have a manual prop valve from Wilwood. I can certainly throw that on there. But to convert Back to Drums... thats a tuff pill to swallow. I think I would buy a few cylinders and put them in a clamp and test that setup 1st to see if it made a difference.

I am supper lost with these issues. But please tell me, how could a prop valve cause this issue?
 

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so did you fill and "bleed" the hydroboost yet?

IDK what the hydroboost 411 is in their instructions for "bleeding"....but typically on PS you raise the front of car so tires are off ground, run engine & PS and turn wheel lock to lock several times...watch for bubbles/foam in reservoir and add fluid if needed

FWIW this PDF states the step about turning wheels lock to lock

12905_930439_san73 (cardone.com)

EDIT: further reading indicates not to run engine initially to bleed....just turn wheel with tires raised off ground

Hydroboost System Bleeding Instructions, Tech Tip - Lares Corporation
 

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Here’s a link…..seems a bit excessive but these guys sell this stuff so you be the judge.
The hydro boost may be the primary reason for your low pedal.
 

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I don't think you'll know for sure how firm the pedal is or isn't until you fire it up and bleed the hydro-boost. As John said in post #55 "I’m not sure that the hydraboost system will resemble manual brakes when not filled. Same as vacuum boosted aren’t just like manual without the vacuum line hooked up." When you say "prop valve" I assume you're referring to a "combination valve". Not a true separate adjustable proportioning valve. You could try blocking off the rear port to see if the pedal firms up. Process of elimination. Personally I'd start with bleeding the hydro-boost. On a few rare occasions I've had to bleed the brakes on a power system with the motor running.
 

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I have a manual prop valve from Wilwood. I can certainly throw that on there. But to convert Back to Drums... thats a tuff pill to swallow. I think I would buy a few cylinders and put them in a clamp and test that setup 1st to see if it made a difference.

I am supper lost with these issues. But please tell me, how could a prop valve cause this issue?
I’m not saying to go back to drums. I’m saying get better discs.

I don’t trust those combo proportioning valves. How can one valve work for all front rear combinations with the correct bias. Answer is they cannot….

Anyway no shortage of opinions and ideas in this thread… 🍿

Don
 

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I don’t trust those combo proportioning valves. How can one valve work for all front rear combinations with the correct bias. Answer is they cannot….

… 🍿

Don
Yeah PV are not one size fits all but a "brake kit" inclusive of MC/Booster/PV along with either just front disc or a 4's if it is that kind of kit...the "included" PV should support whatever combo the kit is composed of.

My Right Stuff all drum, power brake, to front disc swap came with new MC/Booster and "combo" PV. Works great.

I think the Op's issue is more about bleeding his hydroboost system. But his "kit" may not have the most compatible components (calipers) to make it work as one would expect.

I know the combo valve for my Right Stuff disc/drum is different part # than the disc/disc one....ideally OP has confirmed his combo valve is disc/disc

Also my disc/drum MC is 1 1/8" bore which is what OP says his is. Should provide more fluid per stroke than a 1"
 

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The Cadillac calipers are OK if they’re set up right after all GM put these on thousands and thousands of 6000 pound Cadillacs without issues for decades
 

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Discussion Starter · #73 ·
I have confirmed the parts I ordered from right stuff was a disk/disk proportion valve. I have not looked for the part number on the valve itself. I can do that. Once I get time to work on it again I plan to make a few adjustments, I will look for that part number, and I am going to bleep the hydroboost system.

I need to make a spread sheet to keep up with all these ideas lol.

What other rear disk kits are possible better options than the cadillac caliper kits?
 

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The issue with the prop valve isn't disc/disc, it's the calibration. The purpose of the valve is to balance the braking force sent to the front and rear brake pairs. On a factory car, they know the weight distribution and front/rear braking effectiveness, and the tires, etc, etc, so they can build one prop valve that is calibrated for that situation. On your build, you need an adjustable proportioning valve, so that you can tune the braking force between the front and rear pairs so they work together most effectively. The home-grown way to adjust it is to find some deserted road and slam on the brakes, and keep adjusting the valve so the rears are locking up just a little before the fronts. (I'm sure there's a better way to do it, but that's what I've done.)
 

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The issue with the prop valve isn't disc/disc, it's the calibration. The purpose of the valve is to balance the braking force sent to the front and rear brake pairs. On a factory car, they know the weight distribution and front/rear braking effectiveness, and the tires, etc, etc, so they can build one prop valve that is calibrated for that situation. On your build, you need an adjustable proportioning valve, so that you can tune the braking force between the front and rear pairs so they work together most effectively. The home-grown way to adjust it is to find some deserted road and slam on the brakes, and keep adjusting the valve so the rears are locking up just a little before the fronts. (I'm sure there's a better way to do it, but that's what I've done.)
I think you meant to say the fronts need to lock up before the rears?
It would be ideal if all four would lock up simultaneously, but this is hard to achieve. If you lock the rears first you are going into a spin.
 

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Discussion Starter · #76 ·
The issue with the prop valve isn't disc/disc, it's the calibration. The purpose of the valve is to balance the braking force sent to the front and rear brake pairs. On a factory car, they know the weight distribution and front/rear braking effectiveness, and the tires, etc, etc, so they can build one prop valve that is calibrated for that situation. On your build, you need an adjustable proportioning valve, so that you can tune the braking force between the front and rear pairs so they work together most effectively. The home-grown way to adjust it is to find some deserted road and slam on the brakes, and keep adjusting the valve so the rears are locking up just a little before the fronts. (I'm sure there's a better way to do it, but that's what I've done.)
OK - I understand what you are saying. Let me ask you this, Will that change the peddle feel? With the peddle get stiffer sooner in the travel with a manual Prop Valve Adjusted as you said?
 

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I think you meant to say the fronts need to lock up before the rears?
It would be ideal if all four would lock up simultaneously, but this is hard to achieve.
Yes, my bad, you are correct. Ideal is for both front and rear lock at the same time, but fronts can be a little earlier. (It's been a while since I did that)

OK - I understand what you are saying. Let me ask you this, Will that change the peddle feel? With the peddle get stiffer sooner in the travel with a manual Prop Valve Adjusted as you said?
Worst case, you could use the prop valve to identify if the problem is in the front or rear. Crank it all the way so that all the pressure is going to the fronts and check the pedal, then crank it all the other way to check the pedal with just the rears. Otherwise, it shouldn't affect the pedal feel, just how much pressure is going to the front and rear pairs.
 

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Discussion Starter · #78 ·
Looks Like we making some headway with this. I bin working so I was not able to mess with the car until today.

I have started to bleed the power steering system. There is still air in there and we are working to try and get it out. Started with a vacuum pump and then we went to the manual method of turning the steering wheel and pumping the brakes. We are getting there but still for sure air in the steering box! (no difference in the peddle feel)

I ordered new lines for the back so after that everything will be steel braided and all hard lines will be NEW. Have not come in yet.

There is still some adjustment that needs to be mail to the peddle under the dash but I just haven't got to it yet.

SO, My wife tells me her dad was a mechanic in the Army for 22 years and he still works as a mechanic to this day. He actually works as a service guy for a fleet of ambulances right now. Of course I knew he was a mechanic, we talk cars all the time. She says ask my Dad maybe he can help. I called him and he suggest to bleed the master where the lines connect in case there is an air bubble. I figured its worth a shot and while doing that I was looking at the angle of the MC. I was thinking even if there was an air bubble - its on such a steep angle it will never get to the lines. Then I had the brilliant Idea to jack up the back of the car and try to level the MC while bleeding at those lines. As crazy as that sounds I got a decent amount of air out and the peddle is much Improved. I guess the Idiot who bench bled it did a sucky job...

My current plan it to remove the MC - Bench bleed again and try not to fubar it up this time. Adjust the peddle under the dash again. Replace all those lines I have coming in and vacuum bleed the entire system again! I have NO idea how a reverse bleed would work on our cars as the master would capture all that air and you would get a soft peddle like I have bin fighting....

Still gota get the air out of the power steering/hydro boost system also but that's a different thing all together.

If anyone is still reading - Has anyone else had issues with the steep angle of the Master Cylinder? Its actually messing with the level of the brake fluid in the MC because the angle is so bad.
 

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I have not had that problem, but it makes sense. Bench bleeding at this point is probably futile. Now that you know the air is trapping there, bleed the brakes with the rear up like you just did. Can't hurt.
 
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