Re: Which Proportioning valve for 4 wheel disc
[Re: AndyF]
#2483921
04/16/18 10:45 PM
04/16/18 10:45 PM
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Posts: 361 mississippi
lostdog
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Can of worms type of question. You don't need a prop valve with 4 wheel disc brakes since you don't have rear drums. The prop valve "blows off" the pressure to the rear drums so they don't lock up. Drum brakes are non-linear while disc brakes are linear which is why the rear drums need the blow off valve.
Now having said that, lots of people do put a prop valve in a 4 wheel disc setup so they can adjust the rear braking. But that only works if the car is set up with a rear bias to start with. If the car has a front bias on the brakes and you dial down the rears even further then all you are doing is killing the brake effectiveness.
Confused yet?
Bottom line nobody can tell you what to do since we have no idea what you're working on. To properly design a 4 wheel disc system you need to know the weight distribution of the car and the types of brakes and what the static proportioning is front to rear and bunch of stuff like that. Yeah, I don't either and all of that just blew right over my head. But I have stock single piston calipers on the front with 11" discs with el budget disc on the rear. The master cylinder is stock style with two resivoir. I haven't considered creating a bias and honestly I'm not sure I would since I'll really just be cruising. This is helping though and maybe you can help me get them working ! But if I don't need the valve, can I plumb them front/front , rear/rear and get braking without the valve?
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Re: Which Proportioning valve for 4 wheel disc
[Re: lostdog]
#2484973
04/19/18 09:28 AM
04/19/18 09:28 AM
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Joined: Jan 2003
Posts: 313 nj
MoJoe
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You could start by carefully adjusting the bends, then replace the fittings on the new lines with the correct ones for your existing valve. I would assume that as long as you have a decent master cylinder and a distribution valve it should work. I have recently learned that there is a hold off valve for the back brakes on later models with 4 wheel disc brakes. In lieu of that adding a proportioning valve would also give you the opportunity to fine tune the system if you have to. I know it is a pain to change them but what I also always do; is make sure that the master cylinder has the word "disc" somewhere in the description when converting to disc brakes as well. I'm sure it is better to have more than less, so when it comes to brakes, I think its the only time that wearing a belt and suspenders makes sense.
Last edited by MoJoe; 04/19/18 09:35 AM.
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Re: Which Proportioning valve for 4 wheel disc
[Re: lostdog]
#2485224
04/19/18 07:13 PM
04/19/18 07:13 PM
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Joined: Jan 2003
Posts: 1,482 Lake Orion, MI
goldduster318
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What car has a hold-off valve with rear disks? I don't remember seeing this ever. My family happened to own some non-ABS rear disk cars (GM W-bodies) and there is no valve of any kind present.
Now going to personal experience from swapping from 11.75 disk front and 10x2.5" drum rear to the Dr Diff Mustang Cobra 13" Front Disk and 11.75" Disk rear that I opened my adjustable proportioning valve completely and there is absolutely no brake bias issue of any kind.
Not sure what rear disks you bought but if they are the Olds Toronado calipers I usually see on budget ones, the pistons might be a little bigger than they need to be. An adjustable valve and nothing else (other than maybe a drum distribution block to make the tees) should be fine.
'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
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Re: Which Proportioning valve for 4 wheel disc
[Re: lostdog]
#2485515
04/20/18 11:27 AM
04/20/18 11:27 AM
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Joined: Jan 2003
Posts: 313 nj
MoJoe
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I actually agree with the whole just put it together and go...see what happens. I'd rather see the extra parts in the system before it is filled and bled though... taking it apart again it is messy and bleeding the system can be challenging at times. I looked up the rear hold off valve and found that it came on "all 67-70 cars with the Kelsy Hayes 4 wheel disc brake option and high performance engines". I converted a 69 roadrunner front wheel discs, using a disc drum master without a purportioning valve and it worked great. This time around I"ll be adding one as I cut the rear break line while relacing the front frame rail. I have one and figure it to be an easy way to splice the line and have it if I need it.
Last edited by MoJoe; 04/20/18 11:30 AM.
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Re: Which Proportioning valve for 4 wheel disc
[Re: lostdog]
#2485958
04/21/18 09:05 AM
04/21/18 09:05 AM
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ruderunner
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AndyF is spot on. A properly designed 4 wheel disc system doesn't need a p valve. We need more information on your conversion.
That said, I'd plumb the fronts straight to the master, I'd add an adjustable valve to the rear. Remove any residual pressure valve. You can use a drum drum or disc drum master but you need to keep an eye on fluid level. Disc units have larger reservoirs to accommodate the make up fluid as pads wear vs the drum adjuster to accommodate shoe wear.
Angry white pureblood male
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Re: Which Proportioning valve for 4 wheel disc
[Re: Moparteacher]
#2500089
05/24/18 06:35 PM
05/24/18 06:35 PM
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Joined: Jan 2003
Posts: 1,255 Columbus, GA
Michael Ecks
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A further consideration is that you may already have a prop valve incorporated in your combination valve. If they car came from the factory with front disc and rear drum, and the car has the factory combo valve, then it's possible a prop valve is already installed. Which you should correct before you start bending on those shiney new lines. If your car came with disc/drum proportioning valve you need to get a drum/drum distribution block which has a different hard line routing and may acount for why your custom lines don't fit. I know Dr.Diff sells them, I'm sure there are other sources as well.
"The happiness of your life depends upon the quality of your thoughts" ~ Roman Emperor Marcus Aurelius
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Re: Which Proportioning valve for 4 wheel disc
[Re: MoJoe]
#2502338
05/30/18 05:41 PM
05/30/18 05:41 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
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I looked up the rear hold off valve and found that it came on "all 67-70 cars with the Kelsy Hayes 4 wheel disc brake option and high performance engines". There are no 4 wheel disc brake cars from 67-70, unless you are talking about a different manufacturer. A hold off valve is used in disc/drum systems to prevent pressure to the discs until a set pressure is generated int he rear system. this is to overcome the spring pressure holding hte shoes in place and overcome the very slight gap between the shoes and drum. Theoretically, this would allow the shoes and pads to apply simultaneously. The hold off valve is not used in a 4 wheel disc system.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Which Proportioning valve for 4 wheel disc
[Re: AndyF]
#2509431
06/16/18 08:22 PM
06/16/18 08:22 PM
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Posts: 1,404 northeast ohio
hulmule
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Then why dont we use A body disc brakes on the rear of an 8 3/4?
1969 Dodge Coronet R/T Convertible 1979 LiL Red x2 2012 Yellow Jacket 2006 mega cab 1977 Trailduster 1979 Trailduster
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Re: Which Proportioning valve for 4 wheel disc
[Re: lostdog]
#2509453
06/16/18 10:34 PM
06/16/18 10:34 PM
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Joined: Dec 2009
Posts: 339 Gilroy,CA.
mopardude318
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so, if a person has all new wilwood 12.19 brakes with the dynapro 4 piston calipers on all 4 corners, wouldn't a wilwood master cylinder and prop valve kit be good to go? something like this? vvv https://www.summitracing.com/parts/wil-261-13269this is what I plan to use, please tell me I could be okay? This is a small block A body car, street/strip.
408 Stroker 533 HP 520 FT LBS...........................1970 Dart RMS AlterKation
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Re: Which Proportioning valve for 4 wheel disc
[Re: hulmule]
#2509530
06/17/18 09:16 AM
06/17/18 09:16 AM
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Posts: 14,889 up yours
Supercuda
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Then why dont we use A body disc brakes on the rear of an 8 3/4? Why don't you look into that and tell us why.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Which Proportioning valve for 4 wheel disc
[Re: mopardude318]
#2509684
06/17/18 06:18 PM
06/17/18 06:18 PM
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Joined: Nov 2004
Posts: 25,050 Texas
GoodysGotaCuda
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so, if a person has all new wilwood 12.19 brakes with the dynapro 4 piston calipers on all 4 corners, wouldn't a wilwood master cylinder and prop valve kit be good to go? something like this? vvv https://www.summitracing.com/parts/wil-261-13269this is what I plan to use, please tell me I could be okay? This is a small block A body car, street/strip. That's what I have [6piston front/4rear], figure out what bore you want, however.
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Re: Which Proportioning valve for 4 wheel disc
[Re: mopardude318]
#2510275
06/19/18 02:57 AM
06/19/18 02:57 AM
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Joined: Jan 2003
Posts: 30,995 Oregon
AndyF
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so, if a person has all new wilwood 12.19 brakes with the dynapro 4 piston calipers on all 4 corners, wouldn't a wilwood master cylinder and prop valve kit be good to go? something like this? vvv https://www.summitracing.com/parts/wil-261-13269this is what I plan to use, please tell me I could be okay? This is a small block A body car, street/strip. If you have the same rotors and calipers on all four corners you'll be in a world of hurt in a panic stop. I'm not sure a prop valve is going to be able to save you.
Last edited by AndyF; 06/19/18 02:57 AM.
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Re: Which Proportioning valve for 4 wheel disc
[Re: AndyF]
#2510407
06/19/18 02:59 PM
06/19/18 02:59 PM
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Joined: Dec 2009
Posts: 339 Gilroy,CA.
mopardude318
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so, if a person has all new wilwood 12.19 brakes with the dynapro 4 piston calipers on all 4 corners, wouldn't a wilwood master cylinder and prop valve kit be good to go? something like this? vvv https://www.summitracing.com/parts/wil-261-13269this is what I plan to use, please tell me I could be okay? This is a small block A body car, street/strip. If you have the same rotors and calipers on all four corners you'll be in a world of hurt in a panic stop. I'm not sure a prop valve is going to be able to save you. well I'll be damned. I bought all this stuff quite a while ago. Now I'm finally putting everything together. LOL. I guess, if nothing else, I could go to a 13 or 14 inch rotor on the front, along with a 6 piston caliper. Would you say that will maybe solve my predicament? And by definition of the word, "a difficult, unpleasant, or embarrassing situation" is exactly how I feel now...
408 Stroker 533 HP 520 FT LBS...........................1970 Dart RMS AlterKation
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