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Alternative prop. valve plumbing "?"
#1116027
11/18/11 05:36 AM
11/18/11 05:36 AM
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Joined: Aug 2004
Posts: 8,087
Elk Grove, Calif.
bigblock340power
OP
master
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OP
master
Joined: Aug 2004
Posts: 8,087
Elk Grove, Calif.
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I was at my friends shop today talking about the problem I am having with my prop./distribution valve. Now, he's a big Chebby guy and has done some very nice cars through the years. But a cars a car, right? He was telling me I should just skip the factory prop. valve altogether. In the front line,(K/H discs) go directly from the master cylinder to the calipers. In the rear line, plumb in an adjustable prop. valve, so as to be able to adjust the line pressure to the drums. He said he's done this to many a car. Works just fine. Anyone ever done this or heard of it being done? If so, what's your experience? Good or WTH are you talking about you crazy SOB?????
Thank you.
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Re: Alternative prop. valve plumbing "?"
[Re: bigblock340power]
#1116028
11/18/11 08:01 AM
11/18/11 08:01 AM
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Joined: Sep 2003
Posts: 815
PNW
Danan
super stock
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super stock
Joined: Sep 2003
Posts: 815
PNW
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Mike,
Pull your old valve apart. Take a look at if/how the front and rear fluid passages connect with each other. I've pulled lots of these apart on my car and never seen any way for the front and rear passages to "mix". The sole purpose of the distribution valve, as near as I can tell, is a handy place to install spring loaded pistons that, if you lose line pressure, will complete an electrical circuit and light the idiot light on your dash.
I've heard people say that in the event that the rear brakes lose pressure, the piston "shuts off" the fluid going to the rear brakes and diverts it to the front brakes. Or vice-versa; if the front brakes lose pressure it will divert the pressure to the rear. I believe this to be incorrect.
If this WERE the case, why the heck would Chrysler have gone to a two-reservoir master cylinder in 1967 (or whenever that was)? Why not just continue to use the single reservoir system that they had been using for years? It would be cheaper/easier, right?
Chrysler went to a two reservoir system so that if you ripped the brake hose on the rear axle, you would still have your front brakes. The front and rear systems are completely separate and stand alone. Furthermore, this allowed them to build a master cylinder that pressurized the front brakes BEFORE and FASTER than the rear brakes, which lead to better brake performance and safety (less chance of rears locking up and the rear end coming around).
So why would they go to the hassle of creating essentially TWO brake systems, but then CONNECT them at the proportioning valve? Makes no sense...
I'm with your buddy on this; there is no reason why you can't/shouldn't just bypass the valve and connect the front brake line (off the master cylinder) to a brass Tee block that splits the pressure to the left and right wheels, and connect the rear brake line off the MC to the hard line that runs to the rear axle.
Except, of course, that this would be a substantial deviation from how the car was originally constructed, if originality is important to you. You and I see eye to eye on this; build the car the way we want, keeping it looking generally stock, but doing nothing that couldn't be quickly and inexpensively corrected if we desired. This is why we throw the original exhaust manifolds on the shelf and run headers!
OK. So I threw down the gauntlet. I read lots of incorrect/bad advice on the internet, and I don't want to contribute to that. Can someone WHO HAS EXPERIENCE with this validate my experience or tell me where I'm wrong?
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Re: Alternative prop. valve plumbing "?"
[Re: dennismopar73]
#1116031
11/18/11 10:26 AM
11/18/11 10:26 AM
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Joined: Aug 2004
Posts: 8,087
Elk Grove, Calif.
bigblock340power
OP
master
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OP
master
Joined: Aug 2004
Posts: 8,087
Elk Grove, Calif.
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Quote:
I don't run a prop valve , but I have seperate line front and back
car stops great , no issues
Did you run a adjustable prop, valve for the rear?
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Re: Alternative prop. valve plumbing "?"
[Re: dennismopar73]
#1116034
11/18/11 10:29 PM
11/18/11 10:29 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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Anyone who tells you that you do not need a factory combination valve in a disc/drum setup has no clue how a braking system works and does NOT have a braking system that stops just fine.
Get a book on braking system or find an FSM that will explain to you what each part of a combination valve does and Danan you are going to get someone killed with your ignorance.
A factory combination valve, what most people mistakenly refer to as a proportion valve performs 4 functions.
1, pressure differential, this is what Danan was confused about. All pressure differential does is light up an idiot light to tell you that you lost pressure in one side of the brake system. In the old single reservoir setup no brake pedal pressure told you that, well no brakes too.
2. hold off, this delays application of the discs until the shoes are touching the drums
3. metering, this decreases the rate or pressure increase to the rear drums. Modern drum brakes are self energizing, this means that as they actuate they tend to dig in harder on their own and if you do not back off on the pressure increase they will lock up.
4. proportioning, this limits the flow and pressure applied in a panic stop. In normal operation it rarely comes into play. Aftermarket adjustable proportioning valves are not true proportioning valves but rather a pressure regulator that limits maximum pressure. True proportioning valves use the disc pressure as a reference to control the rear pressure, something an aftermarket adjustable valve cannot do as it is only plumbed into the real line and has no reference.
So the next time someone tells you that you do not need a combination valve and that an aftermarket adjustable valve "works fine" you will understand their full lack of their knowledge.
Just remember this is only applicable to a disc drum setup, not an all disc or an all drum setup.
Last edited by Supercuda; 11/18/11 10:45 PM.
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: Alternative prop. valve plumbing "?"
[Re: Supercuda]
#1116035
11/18/11 11:37 PM
11/18/11 11:37 PM
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Joined: Dec 2007
Posts: 18,157
Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,157
Mass
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Very well said Supercuda  , unfortunately your info generally falls on deaf ears in these forums when it comes to these brake problems/questions/applications/modifications threads... IMHO that's a nice Duster the OP has, if it was mine, I'd be outfitting it with a rear disc set-up, sized, based on what caliper volume I have upfront, then it would be "OK" to ditch the PV valve, otherwise if your going to keep the antiquated rear drums, get your PV replaced with a properly functioning unit...
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Re: Alternative prop. valve plumbing "?"
[Re: Supercuda]
#1116036
11/19/11 04:27 AM
11/19/11 04:27 AM
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Joined: Sep 2003
Posts: 815
PNW
Danan
super stock
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super stock
Joined: Sep 2003
Posts: 815
PNW
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Supercuda: Re-read the last paragraph of my post above.
I'm ASKING someone to correct me if I'm wrong. I'm interested in what you have to say, but not at all interested in your BS attitude. So if you can set that aside for just a few minutes, maybe we can have a good dialogue here.
1. From your post above, it does not sound like I'm confused at all about the pressure differential function on a combination valve. It fires the idiot light on the dash.
2. How does the valve perform the 'hold off function'? Don't read anything into this; I'm not being a jerk. I'm just asking a question. My understanding was that the hold-off function was performed in the master cylinder through the use of springs in the piston?
3. How does the valve perform a metering function, or asked another way, what is the mechanism within the valve that performs this function? I thought the size (diameter) of the wheel cylinder pistons, in effect, performed this function?
4. Proportioning. Fully on board with your comments on 'adjustable proportioning valves'. My understanding of this function (ie: the term 'proportioning') is that, ultimately, a percentage of the full braking power is directed to the front brakes, and the remaining percentage is directed to the rear. For instance, 70% to the fronts and 30% to the rear. Again, my understanding was that this proportioning was performed in the master cylinder? You seem to be saying that if you measured the pressure in the line from the MC to the valve, it would/could be higher than the pressure from the valve to the wheel cylinder or caliper?
5. I had some significant issues with the brakes on a ramcharger that resulted in my buying a set of Snap-on brake pressure testers. I don't recall the PSI at work here, but it is not insignificant (several hundred PSI).
When I've taken combination/proportioning valves apart, I don't recall seeing anything inside that would perform these functions.
That said, I'm literally on the other side of the world from a valve OR a FSM. In a brief synopsis would you review the inside of a valve for me? I'm very interested in this topic, and I hear a lot of BS thrown around on the internet. You sound like you know what you're talking about, and I'm willing to listen.
Incidentally, I don't rely on ignorance to kill people. I use my intellect, skill, experience, and cunning.
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Re: Alternative prop. valve plumbing "?"
[Re: Supercuda]
#1116037
11/19/11 11:24 AM
11/19/11 11:24 AM
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Joined: Nov 2009
Posts: 2,177
ill
dennismopar73
top fuel
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top fuel
Joined: Nov 2009
Posts: 2,177
ill
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Quote:
Anyone who tells you that you do not need a factory combination valve in a disc/drum setup has no clue how a braking system works and does NOT have a braking system that stops just fine.
Get a book on braking system or find an FSM that will explain to you what each part of a combination valve does and Danan you are going to get someone killed with your ignorance.
A factory combination valve, what most people mistakenly refer to as a proportion valve performs 4 functions.
1, pressure differential, this is what Danan was confused about. All pressure differential does is light up an idiot light to tell you that you lost pressure in one side of the brake system. In the old single reservoir setup no brake pedal pressure told you that, well no brakes too.
2. hold off, this delays application of the discs until the shoes are touching the drums
3. metering, this decreases the rate or pressure increase to the rear drums. Modern drum brakes are self energizing, this means that as they actuate they tend to dig in harder on their own and if you do not back off on the pressure increase they will lock up.
4. proportioning, this limits the flow and pressure applied in a panic stop. In normal operation it rarely comes into play. Aftermarket adjustable proportioning valves are not true proportioning valves but rather a pressure regulator that limits maximum pressure. True proportioning valves use the disc pressure as a reference to control the rear pressure, something an aftermarket adjustable valve cannot do as it is only plumbed into the real line and has no reference.
So the next time someone tells you that you do not need a combination valve and that an aftermarket adjustable valve "works fine" you will understand their full lack of their knowledge.
Just remember this is only applicable to a disc drum setup, not an all disc or an all drum setup.
Well,, mmm the pressure for brakes is set up thru the master cyl!
all the prop valve does is seperate the two systems,THAT'S ALL IT DOES! the low pressure in turn, turns the brake lite on indicating there is a issue with the brake system! thus the spring and seals you see inside the prop valve.
your quote; So the next time someone tells you that you do not need a combination valve and that an aftermarket adjustable valve "works fine" you will understand their full lack of their knowledge.
My brake systems are of disk drum setups.
OOO young grasshopper, you have allot to learn yet
By the way, nothing wrong with having a prop valve, makes it easy to seperate the front lines, hahahalol
 
Last edited by dennismopar73; 11/19/11 11:28 AM.
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Re: Alternative prop. valve plumbing "?"
[Re: dennismopar73]
#1116038
11/19/11 11:42 AM
11/19/11 11:42 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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All I can add is I have a 65 dart with 74 A discs w semi metallic pads and 10" drums with parts house cheap linings on a 7&1/4" and a large bore alum M/C (1&1/8 iirc) and I plumbed it into the OE 9" 4 wheel drum splitter and I have no issues. On paper everything is wrong here. Stops good/no excessive front pad or rotor wear/pedal effort not bad & rears locked up once when I was paying more attention to the eye candy on the sidewalk than to the distance to the car in front of me. I do drive everyday but I concede the speeds around Lincoln are pretty tame so in a more agressive environment I may have probs. I had read once that a metering valve is good as it holds off psi to the front till the rear drums pretty much make contact to lessen excessive front pad wear but I have not had a prob. I would add a adj prop valve in the rear or smaller cyls if I was starting from scratch & wanted less (rear) lockup. Not trying to add fuel to the fire just relating my personal experiences with this
live every 24 hour block of time like it's your last day on earth
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Re: Alternative prop. valve plumbing "?"
[Re: dennismopar73]
#1116039
11/19/11 12:00 PM
11/19/11 12:00 PM
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Joined: Jan 2003
Posts: 338
Montreal Quebec
STROKIE
enthusiast
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enthusiast
Joined: Jan 2003
Posts: 338
Montreal Quebec
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I almost complete my front disc brake conversion... Must I use combination valve or not? Mopar Action on line http://www.moparaction.com/tech/archive/disc-main.html As per Mopar Action on line, said the text below, Some factory installations, notably C-body and later B-body cars, used a “combination” valve, which also included a front-brake metering valve. Its function was a allow the rear brakes to achieve some minimal line pressure (against the return springs) before the fronts began to apply. This was supposed to reduce the possibility of the fronts locking up first on glare ice. Don’t worry about this, besides, with the rears locked first, the car must spin. In addition, none of these valves are no longer available new, repops are from who-knows-where, and most available junkyard samples all seem to be made of cast iron (instead of brass) so they’re rust city. Again, your best bet is to just leave your stock “tee / switch” assembly unmolested and plumb in an adjustable valve in the rear line, as we’ve done in our swap. I don't know wich way to go... 
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Re: Alternative prop. valve plumbing "?"
[Re: STROKIE]
#1116041
11/19/11 12:37 PM
11/19/11 12:37 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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Quote:
I almost complete my front disc brake conversion...
Must I use combination valve or not?
Mopar Action on line http://www.moparaction.com/tech/archive/disc-main.html
As per Mopar Action on line, said the text below,
Some factory installations, notably C-body and later B-body cars, used a “combination” valve, which also included a front-brake metering valve. Its function was a allow the rear brakes to achieve some minimal line pressure (against the return springs) before the fronts began to apply. This was supposed to reduce the possibility of the fronts locking up first on glare ice. Don’t worry about this, besides, with the rears locked first, the car must spin. In addition, none of these valves are no longer available new, repops are from who-knows-where, and most available junkyard samples all seem to be made of cast iron (instead of brass) so they’re rust city. Again, your best bet is to just leave your stock “tee / switch” assembly unmolested and plumb in an adjustable valve in the rear line, as we’ve done in our swap.
I don't know wich way to go...
My opinion of Ehrenberg's brake knowledge is this, Larry knows more than Rick.
Many inaccurate statements and plain wrong details. Chrysler's engineers, and ALL other OEM engineers, did not come up with almost identical solutions to the disc/drum brake system idiosyncrasies as part of one giant conspiracy. They came up with these solutions because the problem is the same regardless of who's name is on the vehicle, and the solutions will be very similar.
So when some internet (or magazine) clown says "you don't need it" he is wrong. Hundreds of engineers with more knowledge, more experience and more resources than ANYONE, me included, on this site all agree it's a necessity.
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: Alternative prop. valve plumbing "?"
[Re: Supercuda]
#1116042
11/19/11 12:56 PM
11/19/11 12:56 PM
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Joined: Nov 2009
Posts: 2,177
ill
dennismopar73
top fuel
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top fuel
Joined: Nov 2009
Posts: 2,177
ill
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Many inaccurate statements and plain wrong details. Chrysler's engineers, and ALL other OEM engineers, did not come up with almost identical solutions to the disc/drum brake system idiosyncrasies as part of one giant conspiracy. They came up with these solutions because the problem is the same regardless of who's name is on the vehicle, and the solutions will be very similar. So when some internet (or magazine) clown says "you don't need it" he is wrong. Hundreds of engineers with more knowledge, more experience and more resources than ANYONE, me included, on this site all agree it's a necessity. By law they had to do it!!! Plus the company that built them got a very large contract (money) to build them for all the cars makers, so please , don't try to put more into what is really not there! as for my educational background on brakes is high, beside book smart don't make you smart, makes you a smart azz If you like your prop valve , then by all means run it, , after all those engineers got paid allot of money just so you could have it on you're vehicle . right along with the egr valves ,cat converters air pumps ets, those engineers got that right ! ha ha ha lol
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Re: Alternative prop. valve plumbing "?"
[Re: Supercuda]
#1116043
11/19/11 12:57 PM
11/19/11 12:57 PM
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Joined: Oct 2010
Posts: 183
Eden, Texas
Strawdawg
member
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member
Joined: Oct 2010
Posts: 183
Eden, Texas
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So, are you saying that the car will not try to change back for front when the rears lock up first?
Steve
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Re: Alternative prop. valve plumbing "?"
[Re: Strawdawg]
#1116045
11/19/11 01:22 PM
11/19/11 01:22 PM
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Joined: Nov 2009
Posts: 2,177
ill
dennismopar73
top fuel
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top fuel
Joined: Nov 2009
Posts: 2,177
ill
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Quote:
So, are you saying that the car will not try to change back for front when the rears lock up first?
what I'm saying is the type of master cyl for your application create the pressure for the front and rears, different stroke lenghts inside the cyl is where it's at, also sizing of pistons
what the heck do I know, I'm just a freaking clown!
lets try this, say you have a stock system that everyone has, you want more pressure to the rear, so you buy a adj valve put it in do you put it in after the prop valve or before? If you put it in after how in the world , if what he says is true , then how can you get more pressure?
In the old days of 1 line master cyl you had same pressure front and rear, safty gurus decided after several brake line failures and deaths, the system needed to be seperated and a 2 line master cyl evloved . and also it was required that the system needed a warning that would tell the driver when something was wrong with that system thus the prop valve it help in 2 ways , it seperate the front and back , and serves as a warning lite activator.
after that I'm uneducated lol
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Re: Alternative prop. valve plumbing "?"
[Re: Supercuda]
#1116046
11/19/11 02:01 PM
11/19/11 02:01 PM
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Joined: Oct 2010
Posts: 183
Eden, Texas
Strawdawg
member
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member
Joined: Oct 2010
Posts: 183
Eden, Texas
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Quote:
Quote:
So, are you saying that the car will not try to change back for front when the rears lock up first?
How did you even get close to that from what I said?
I realize that you never miss a chance to take a pot shot at whatshisname, but, I believe one of the reasons he gave for using an aftermarket valve, beyond the difficulty in finding a replacement stock valve that works as designed, is the tendency for some models to lock the rears which can be very dangerous as the rear end accelerates when the tires lock.
Add the mods we do to cars such as adding larger tires which increase rear braking, adding larger rear drums, etc, and we can easily justify replacing the stock valve with an adjustable valve to get the front/rear braking in sync.
Mopar used two basic m/c proportioning ratios according to the literature. One with 69/31% distribution and the other, I believe, was 67/33%.
This leaves us with trying to play with wheel cylinder size or an adjustable valve after we start changing up things with regard to brake size, brake composition, tire size/tread composition, and spring rates, etc.
Give the number of variables available to us today, I personally think that an adjustable valve is the easiest means of dialing in braking, but, opinions will surely variable.
Sorry, that I had difficulty discerning technical intent from within your rant.
Steve
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