G-Body Disc Disc Proportioning Valve Question

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L92 OLDS

Comic Book Super Hero
Mar 30, 2012
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West Michigan
When I converted my GP to 4 wheel disc I used a prop valve from an 83 or 84 el Dorado , since they are a similar size and weight to a Gbody, and it worked perfectly. A Toronado or Riviera of the same vintage with 4 wheel disc would also be the same.

I also am running a factory Cadillac Seville prop valve with no issues.
 
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7883Elko

n00b
Aug 7, 2018
3
1
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Yup I just have the QP base disc kit except they are the calipers w/o e brakes...I went ahead and ordered a disc disc prop valve for now and will probably end up swapping to a larger master cylinder bore in the near future..Thanks everyone for the input! fleming442 do you have a QP 9"? Was wondering how it's holding up I haven't talked with anyone that owns one yet
 

fleming442

Captain Tenneal
Dec 26, 2013
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Yup I just have the QP base disc kit except they are the calipers w/o e brakes...I went ahead and ordered a disc disc prop valve for now and will probably end up swapping to a larger master cylinder bore in the near future..Thanks everyone for the input! fleming442 do you have a QP 9"? Was wondering how it's holding up I haven't talked with anyone that owns one yet
No, my buddy just put one in his C10 project; it's still in fab; so no use yet. I learned about those stupid Seville calipers on another friend's 71 Z28- we bled the brakes for 3 days!
 
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spidereyes455

G-Body Guru
Mar 6, 2013
776
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Northeastern PA
Also when I converted my GP I used blazer brakes front and rear (so I could still use 15in wheels) I initially used the el dorado master cylinder but was not happy with the pedal travel so I switched to a master for a 81 T/A with 4 wheel disc since its a larger bore than the caddy and its an aluminum cylinder so it looks like a stock Gbody one and also required no swapping around of the brake lines. Now the car really stops on a dime and gives 9 cents change. The only thing I may do still is swap out to a B body booster since there doesn't seem to be enough power assist for my liking now.
 
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el camino ss 84

Master Mechanic
Oct 23, 2016
377
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Nw okc
For my elcamino disc brake setup I used Cadillac eldorado master cylinder and portioning valve and rear disc setup with blazer front brakes.
 

GBodyscuffle

Master Mechanic
May 24, 2014
349
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Keysville, VA
I'm struggling with the same issue at the moment. I have a qp 9" with the explorer brakes with the e brake. I replaced prop valve with the stock style one from summit thats "supposed" to work with disc/disc. So far I can only get a trickle from the rear brakes. Front has a pretty good flow of fluid. Followed the instructions with the valve and still isn't working. May just be making a stupid error somewhere but i've never had so much trouble bleeding brakes. Any ideas? And sorry to hijack the post.
 

Doug Chahoy

Comic Book Super Hero
Nov 21, 2016
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I have to say this thread gives ALOT of info. But with such conflicting opinions/experiences, I'm BAFFLED.
I plan in the next 6 mos. to do the QP9 swap. I already have 2000 era Camaro 4 wheel discs with E brake sitting in my basement.
My mind is leaning toward the 81 TA master. Other than that brass prop valve, wouldn't an 81 TA prop valve work?
I want to have ALL the right/best parts before I even start.
 

84GP455

G-Body Guru
Jun 19, 2007
779
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28
Methuen Ma.
To answer your question, yes a 1981 TA prop valve will work as long as the application is for rear discs.
 
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