Moparts
Alternative prop. valve plumbing "?"
Posted By: bigblock340power
Alternative prop. valve plumbing "?" - 11/18/11 09:36 AM
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.
Posted By: Danan
Re: Alternative prop. valve plumbing "?" - 11/18/11 12:01 PM
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?
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 11/18/11 02:21 PM
Hi Danan, how you doing? Having more fun than you deserve, I'd wager!
I see your point here. But you know how good I can be at hiding things like this. But I now have an original K/H 232 O X prop. valve I rebuilt and am getting ready to put on the car. I forgot about the one Craig gave me years ago from his sons "first car" driving fiasco. It came off a Duster identical to mine in the braking department and year. That's the one in the picture brake down I did for anyone needing it. Jim V. said I could use any of the ones he has too.
Posted By: dennismopar73
Re: Alternative prop. valve plumbing "?" - 11/18/11 02:24 PM
I don't run a prop valve , but I have seperate line front and back
car stops great , no issues
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 11/18/11 02:26 PM
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?
Posted By: dennismopar73
Re: Alternative prop. valve plumbing "?" - 11/18/11 02:33 PM
nope, before 196? the never had them anyways, thew only reason they where ever put on was for safety, it just seperated the 2 systems as stated above, the master cyl does the diff pressure dealings, so i just did away with it , run m,y lines as normal!
Posted By: dennismopar73
Re: Alternative prop. valve plumbing "?" - 11/18/11 02:40 PM
I have zero issues! The car stops great, the rears will lock up just as normal, actually think the brake peddle may be better, just me.
most people who put the adjustable prop , due so because they want a heavy feel to the rear,for road course, etc, or the want to hold the rear at the stating line.
Posted By: Supercuda
Re: Alternative prop. valve plumbing "?" - 11/19/11 02:29 AM
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.
Posted By: DAYCLONA
Re: Alternative prop. valve plumbing "?" - 11/19/11 03:37 AM
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...
Posted By: Danan
Re: Alternative prop. valve plumbing "?" - 11/19/11 08:27 AM
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.
Posted By: dennismopar73
Re: Alternative prop. valve plumbing "?" - 11/19/11 03:24 PM
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
Posted By: RapidRobert
Re: Alternative prop. valve plumbing "?" - 11/19/11 03:42 PM
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
Posted By: STROKIE
Re: Alternative prop. valve plumbing "?" - 11/19/11 04:00 PM
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...
Posted By: Supercuda
Re: Alternative prop. valve plumbing "?" - 11/19/11 04:27 PM
Quote:
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
I learned you don't know carp about brake systems.
Guess that is one less thing I need to learn, thanks.
Posted By: Supercuda
Re: Alternative prop. valve plumbing "?" - 11/19/11 04:37 PM
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.
Posted By: dennismopar73
Re: Alternative prop. valve plumbing "?" - 11/19/11 04:56 PM
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
Posted By: Strawdawg
Re: Alternative prop. valve plumbing "?" - 11/19/11 04:57 PM
So, are you saying that the car will not try to change back for front when the rears lock up first?
Posted By: Supercuda
Re: Alternative prop. valve plumbing "?" - 11/19/11 05:02 PM
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?
Posted By: dennismopar73
Re: Alternative prop. valve plumbing "?" - 11/19/11 05:22 PM
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
Posted By: Strawdawg
Re: Alternative prop. valve plumbing "?" - 11/19/11 06:01 PM
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.
Posted By: Strawdawg
Re: Alternative prop. valve plumbing "?" - 11/19/11 06:05 PM
Quote:
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
LOL...I don't believe you are the clown in question. In essence, I believe you are correct (see my post above).
If you retain the factory valve, the adjustable valve normally goes in the main line running to the rear 
Posted By: Supercuda
Re: Alternative prop. valve plumbing "?" - 11/19/11 06:43 PM
What, exactly, is the law that states cars must have a disc/drum brake setup?
There is none. The law you are vaguely aware of calls for a split braking system so that one leak does not deactivate all the brakes.
None of which has much do do with what we are talking about here. Stop trying to confuse the issue with irrelevancies.
What we are talking about is a device that allows two otherwise incompatible braking systems to function together.
Disc brakes are essentially linear. All wheel discs are fairly easy to balance, only weight shift has an effect on balance in a properly designed system.
Self energizing drums are not linear. All wheel drums are fairly easy to balance, only weight shift has an effect on balance in a properly designed system.
However, combine the two and you have issues with the differences in how they function. That is what a combination valve addresses.
Your commentary on how brakes work, what a proportioning valve does and almost everything else is totally off base and ignorant.
You are not book smart, street smart or any other kind of smart in regards to brakes and if anyone chooses to follow your "advice" I pity them.
Posted By: dennismopar73
Re: Alternative prop. valve plumbing "?" - 11/19/11 08:20 PM
"Your commentary on how brakes work, what a proportioning valve does and almost everything else is totally off base and ignorant.
You are not book smart, street smart or any other kind of smart in regards to brakes and if anyone chooses to follow your "advice" I pity them."
Then please un-educate me !
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 11/19/11 11:07 PM
Quote:
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...
I seem to have started a bit of a firestorm here. Sorry for that, all.
Thanks Dayclona for the complement about my rolling parts house. I thank you all for your advise and opinions. Jim V. has graciously let me use one of his (dare I use this term) prop. valves to see if it's my repop valve that's giving me all the headaches.
To help clear things up a little, I don't think I was ever going to entertain the notion of going without a prop. valve. Basically was just a query. Just thought I'd interject my thoughts here while theirs a lull in the lobbing of criticisms.
Thank you all again. Now lets all play nice.
Posted By: Rick_Ehrenberg
Re: Alternative prop. valve plumbing "?" - 11/23/11 10:06 PM
Quote:
<snip>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.
I have no idea where this split/bias m/cyl info grew from, but I can tell you this: Every muscle-era Mopar I have ever investigated uses a straight-bore master cylinder, 50/50 distribution. Period. This error was fixed in later MP catalogs.
I haven't read everything above, so forgive me if some of this is redundant...just some info and factoids which I hope you find useful...
Combination valves are a combo of the safety switch / tee, a prop valve, and a metering valve. The purpose of the metering (standoff) valve is to prevent the front brakes from applying until the resistance of the rear shoe return springs has been overcome -- to prevent early front wheel lockup on glare ice.
If going to an adjustable prop valve, and you have a block/tee with a built-in prop valve, the stock valve must be "gutted" from the block. You only want one prop valve.
Getting the proportioning close by juggling wheel cylinder / caliper bore sizes is the preferred way to go. Prop valves don't "cut in" until there's a few hundred PSI (varies by model), often too late (!) on slippery surfaces. And you don't ever want both rear wheels locked. (That's why RWAL was introduced).
Factory setups of the '60s and early '70s were compromises. 440 Road Runner coupes used the same prop parts as 6-cyl Satellite wagons, and the F/R weight distribution couldn't be more different. Getting your F/R proportioning dialed in precisely makes a HUGE difference in stopping distances.
Another way to change proportioning is via drum / rotor diameter. Generally, if you swap a '60s / early-70s Mopar to 11.75" cop rotors, you've come close. 7/8" rear wheel cyls., and an adjustable prop valve, and you're within 20 feet or so (from 60 MPH) of a modern ABS performance car.
Lining material / friction coefficient / temperature / tire size / width / tread compound (etc.) also figure into the equation. That's why race cars typically have the prop valve (lever type) where the driver can adjust it during an event!
Bendix Duo-Servo (on almost all '62-'89 RWD Mopars) rear brakes have so much self energizing action that, especially with a power booster, even Mario Andretti would have tough time stopping straight. About all you can do is be on your toes -- literally -- threshold braking.
Rick
Posted By: Strawdawg
Re: Alternative prop. valve plumbing "?" - 11/24/11 12:51 AM
Quote:
I have no idea where this split/bias m/cyl info grew from, but I can tell you this: Every muscle-era Mopar I have ever investigated uses a straight-bore master cylinder, 50/50 distribution. Period. This error was fixed in later MP catalogs.
I haven't read everything above, so forgive me if some of this is redundant...just some info and factoids which I hope you find useful...
Combination valves are a combo of the safety switch / tee, a prop valve, and a metering valve. The purpose of the metering (standoff) valve is to prevent the front brakes from applying until the resistance of the rear shoe return springs has been overcome -- to prevent early front wheel lockup on glare ice.
If going to an adjustable prop valve, and you have a block/tee with a built-in prop valve, the stock valve must be "gutted" from the block. You only want one prop valve.
Getting the proportioning close by juggling wheel cylinder / caliper bore sizes is the preferred way to go. Prop valves don't "cut in" until there's a few hundred PSI (varies by model), often too late (!) on slippery surfaces. And you don't ever want both rear wheels locked. (That's why RWAL was introduced).
Factory setups of the '60s and early '70s were compromises. 440 Road Runner coupes used the same prop parts as 6-cyl Satellite wagons, and the F/R weight distribution couldn't be more different. Getting your F/R proportioning dialed in precisely makes a HUGE difference in stopping distances.
Another way to change proportioning is via drum / rotor diameter. Generally, if you swap a '60s / early-70s Mopar to 11.75" cop rotors, you've come close. 7/8" rear wheel cyls., and an adjustable prop valve, and you're within 20 feet or so (from 60 MPH) of a modern ABS performance car.
Lining material / friction coefficient / temperature / tire size / width / tread compound (etc.) also figure into the equation. That's why race cars typically have the prop valve (lever type) where the driver can adjust it during an event!
Bendix Duo-Servo (on almost all '62-'89 RWD Mopars) rear brakes have so much self energizing action that, especially with a power booster, even Mario Andretti would have tough time stopping straight. About all you can do is be on your toes -- literally -- threshold braking.
Rick
I thought perhaps I had dreamed it up, or it was from a Buick, or such, but, the information is contained in the 9th edition of the Mopar Chassis book by Larry Shepard/Michael Gingerella. I believe this is the latest edition. Pages 347/348
On the other hand, this refers to two specific master cylinders-Part#s P5249270 and P5249271
Therefore, the comment may well be wrong in the general context with regard to the units that came on the cars originally.
Here are a couple of pics...sorry for the fuzziness-too little light at the moment and too much shake, but, I am sure you have the book and can check if you are interested.
Posted By: Strawdawg
Re: Alternative prop. valve plumbing "?" - 11/24/11 12:53 AM
and
Posted By: Strawdawg
Re: Alternative prop. valve plumbing "?" - 11/24/11 03:16 AM
Also, the Mopar adjustable proportioning valve mentioned in the second, unreadable pic is PN P5249088 which is reportedly adjustable from 100-1000 psi which should be adequate in dialing in the rears on a modded car-installed in the line going to the rears.
If you have an original combo valve that is rusted up internally which is pretty common on older valves, then you might consider one like this from Wilwood
http://www.jegs.com/i/Wilwood/950/260-11179/10002/-1?parentProductId=1284815
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 11/24/11 08:02 AM
I have no idea where this split/bias m/cyl info grew from, but I can tell you this: Every muscle-era Mopar I have ever investigated uses a straight-bore master cylinder, 50/50 distribution. Period. This error was fixed in later MP catalogs.
I haven't read everything above, so forgive me if some of this is redundant...just some info and factoids which I hope you find useful...
Combination valves are a combo of the safety switch / tee, a prop valve, and a metering valve. The purpose of the metering (standoff) valve is to prevent the front brakes from applying until the resistance of the rear shoe return springs has been overcome -- to prevent early front wheel lockup on glare ice.
If going to an adjustable prop valve, and you have a block/tee with a built-in prop valve, the stock valve must be "gutted" from the block. You only want one prop valve.
Getting the proportioning close by juggling wheel cylinder / caliper bore sizes is the preferred way to go. Prop valves don't "cut in" until there's a few hundred PSI (varies by model), often too late (!) on slippery surfaces. And you don't ever want both rear wheels locked. (That's why RWAL was introduced).
Factory setups of the '60s and early '70s were compromises. 440 Road Runner coupes used the same prop parts as 6-cyl Satellite wagons, and the F/R weight distribution couldn't be more different. Getting your F/R proportioning dialed in precisely makes a HUGE difference in stopping distances.
Another way to change proportioning is via drum / rotor diameter. Generally, if you swap a '60s / early-70s Mopar to 11.75" cop rotors, you've come close. 7/8" rear wheel cyls., and an adjustable prop valve, and you're within 20 feet or so (from 60 MPH) of a modern ABS performance car.
Lining material / friction coefficient / temperature / tire size / width / tread compound (etc.) also figure into the equation. That's why race cars typically have the prop valve (lever type) where the driver can adjust it during an event!
Bendix Duo-Servo (on almost all '62-'89 RWD Mopars) rear brakes have so much self energizing action that, especially with a power booster, even Mario Andretti would have tough time stopping straight. About all you can do is be on your toes -- literally -- threshold braking.
Rick
Mr. Ehrenberg, I'm glad you chimed in. Let me clarify my question by asking another, and wading past all the high spirited interaction above. I am the OP of this opinion filled, excrement slinging Malay. My '71 340 Duster came with K/H (Power) front four piston caliper disc/rear drum brakes. When I bought the car, the power booster was off it. Everything else was intact, and functioning very well. I even plumed in a line lock and went drag racing (I've removed the line lock during this restore). I replaced the org. MC with your aluminum MC you sell here a few years ago. Still everything stopped just fine. My trouble came when, while restoring the car, I replaced the K/H prop./distribution valve with an after market new one I found being sold by a well known Mopar parts vender. When I got everything back together and tried to stop the car, it just didn't want to stop very well. It felt like I just didn't have enough pressure to the Calipers/ drums to do a good job. I pressure bled the system (twice), and bench bled the MC. The peddle felt great, no slop, or fade. I can power out of the brakes, when fully applied (never been able to do that before). My question: given all the variables I described above, could the prop./distribution valve be the culprit? I have since rebuilt me K/H prop. valve (mostly just cleaning it up real well), and intend to place it back into the system to try it again. What do you think?
Thank you,
mike
Posted By: Rick_Ehrenberg
Re: Alternative prop. valve plumbing "?" - 11/24/11 05:23 PM
Quote:
<snip!> My '71 340 Duster came with K/H (Power) front four piston caliper disc/rear drum brakes. When I bought the car, the power booster was off it. Everything else was intact, and functioning very well. I even plumed in a line lock and went drag racing (I've removed the line lock during this restore). I replaced the org. MC with your aluminum MC you sell here a few years ago. Still everything stopped just fine. My trouble came when, while restoring the car, I replaced the K/H prop./distribution valve with an after market new one I found being sold by a well known Mopar parts vender. When I got everything back together and tried to stop the car, it just didn't want to stop very well. It felt like I just didn't have enough pressure to the Calipers/ drums to do a good job. I pressure bled the system (twice), and bench bled the MC. The peddle felt great, no slop, or fade. I can power out of the brakes, when fully applied (never been able to do that before). My question: given all the variables I described above, could the prop./distribution valve be the culprit? I have since rebuilt me K/H prop. valve (mostly just cleaning it up real well), and intend to place it back into the system to try it again. What do you think?
Thank you,
mike
This Chinese stuff can (and does) have all kinds of bizarre defects. But also be sure that the plumbing to the valve is correct. And, I'd sure bleed one more time -- try a different method, maybe. Remember that the master must be bled before any of the wheels, and if you allow either reservoir to go dry, it must be bled again. I can't visualize a valve defect that would result in a soft pedal, which seems to be what you are describing.
You didn't say whether you re-installed the power booster. If you replaced it, I hope it is one intended for PDB. Otherwise booster runout is a possibility. Me? Manual all the way. Much easier to threshold brake. Threshold braking
Your term "distribution valve" may mislead some. As was mentioned by others above, the front and rear circuits are totally independent and disconnected - fluid NEVER flows from the front circuit to the rear, or vice-versa, under any conditions. The ONLY function of the "valve" (it isn't) on all-drum cars is to turn on the idiot light when there's a pressure differential -- a Federal requirement starting in 1967.
On the master cylinder bias quandary...you'll note that the bore dimension given is singular - meaning, straight bore. There can, therefore, be no pressure differential or proportioning built in to the master (excluding the '90s / 00s stuff with valves that screw right into the master cylinder, of course). I believe those numbers refer to the maximum total volume of fluid that can be pumped from each section of the bore. All that's in a dual-circuit master (at least Mopars) is a primary piston, and a second floating piston. One outlet is between the pistons, the second is behind the secondary piston. Yes, due to friction, etc., there might be a 1% (or less) pressure differential, but that's it! Hook up gauges and see.
The MP masters were just ~'80s truck masters, the later angled-reservoir ones were '90s/00s truck.)
Rick
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 11/25/11 04:49 AM
Thanks again for your reply.
I do not intend to put the power booster back on. I like the feel of the man. brakes (besides, I don't think my cam choice in my 416 would support enough vacuum for it anyway). I did bench bleed the M C before I put it into the system. Then ( I didn't mention this part in the first communiques above) bled the system with my wife (she's a real trooper) pumping the brakes, while I went from wheel to wheel. Then I did the two power bleeds later. I read your suggestions and I think I see what your getting at.
Posted By: MR_P_BODY
Re: Alternative prop. valve plumbing "?" - 11/25/11 06:35 AM
Quote:
Thanks again for your reply.
I do not intend to put the power booster back on. I like the feel of the man. brakes (besides, I don't think my cam choice in my 416 would support enough vacuum for it anyway). I did bench bleed the M C before I put it into the system. Then ( I didn't mention this part in the first communiques above) bled the system with my wife (she's a real trooper) pumping the brakes, while I went from wheel to wheel. Then I did the two power bleeds later. I read your suggestions and I think I see what your getting at.
The so called bias is the reservoir volume(from what
I have been told)... nothing to do with valve bias...
if you look/measure the bore of the master you will
find 1 bore size in there not 2 which would change
the bias... I have been running the alum master on
both my race car and my street rod without any DIST/error
in system valve for years... on the race car I have
disc/disc but with the lines on the master reversed
for the volume(front reservoir to the front brakes, rear to
the rears) with a adjustable valve(prop valve) on the
front brakes.... reason its on the fronts.... the
small tires CANT take the brake force that the BIG
rear slicks can on a pedal spike... quick lesson...
the adjustable prop valve JUST SLOWS THE FLUID...
given enough time the pressure will equal out... so
with the prop on the front tires it slows the spike
and allows the rear tires to do MOST of the braking
(and YES I did work in the brake lab for Chrysler
for some time)... but MOST of my time was in the
fuel and exhaust lab
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 11/25/11 01:32 PM
The so called bias is the reservoir volume(from what
I have been told)... nothing to do with valve bias...
if you look/measure the bore of the master you will
find 1 bore size in there not 2 which would change
the bias... I have been running the alum master on
both my race car and my street rod without any DIST/error
in system valve for years... on the race car I have
disc/disc but with the lines on the master reversed
for the volume(front reservoir to the front brakes, rear to
the rears) with a adjustable valve(prop valve) on the
front brakes.... reason its on the fronts.... the
small tires CANT take the brake force that the BIG
rear slicks can on a pedal spike... quick lesson...
the adjustable prop valve JUST SLOWS THE FLUID...
given enough time the pressure will equal out... so
with the prop on the front tires it slows the spike
and allows the rear tires to do MOST of the braking
(and YES I did work in the brake lab for Chrysler
for some time)... but MOST of my time was in the
fuel and exhaust lab
So, are you telling me I should go ahead and try the suggestion about running without the Prop. valve? Plumbing the way it's suggested in my org. post? Or just letting me know how you've done it, and it does work (for you at least!).
Posted By: MR_P_BODY
Re: Alternative prop. valve plumbing "?" - 11/25/11 03:33 PM
So, are you telling me I should go ahead and try the suggestion about running without the Prop. valve? Plumbing the way it's suggested in my org. post? Or just letting me know how you've done it, and it does work (for you at least!).
I dont tell people how to do anything... what I said
was how I do it and it works very good.... if it
is a street car I would leave it in place... it was
put there for safety
Posted By: Rick_Ehrenberg
Re: Alternative prop. valve plumbing "?" - 11/29/11 04:23 AM
A good discussion of proportioning and valves...
prop valve tech The '60s FSMs called for the valve to output a constant 360 to 405 PSI with a constant 500 PSI input.
At some lower pressure (varies by model, or adjustment on adjustable valves) the rubber "stage" seal does not close, so it is basically straight-thru. Once the set pressure is reached, it is, effectively, a small piston pushing on a larger one, reducing pressure by the ratio of (the area of) one to the other. If it "equalizes", there's internal leakage (which may well be common, since most stops only last a few seconds and these weren't precision implements!)
Again, the bulk of the proportioning was done by the ratio of F/R mechanics and hydraulics, as it should be. On a typical '60s Mopar, the fronts do 60-65% of the work.
Rick
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 12/02/11 04:46 PM
Quote:
A good discussion of proportioning and valves...
prop valve tech
The '60s FSMs called for the valve to output a constant 360 to 405 PSI with a constant 500 PSI input.
At some lower pressure (varies by model, or adjustment on adjustable valves) the rubber "stage" seal does not close, so it is basically straight-thru. Once the set pressure is reached, it is, effectively, a small piston pushing on a larger one, reducing pressure by the ratio of (the area of) one to the other. If it "equalizes", there's internal leakage (which may well be common, since most stops only last a few seconds and these weren't precision implements!)
Again, the bulk of the proportioning was done by the ratio of F/R mechanics and hydraulics, as it should be. On a typical '60s Mopar, the fronts do 60-65% of the work.
Rick
A very interesting read, Rick. Thanks.
I did go back to my stock Prop. valve. I just got done installing it. Bled the system, and it does feel a whole lot better. I have yet to drive the vehicle, but all initial indacations look good. I'll be driving it today. So if you don't read about me in the news, or obituaries, all went well.
Thanks agin to all who helped out.
Posted By: hemi71x
Re: Alternative prop. valve plumbing "?" - 12/02/11 04:51 PM
So Mike,
You must have found the fitting you were looking for on your original prop valve?
Or did you plumb in mine, that you borrowed from me, as a test?
Jim V.
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 12/02/11 06:30 PM
I put another K/H prop. valve in. I didn't use yours. I'll get it back to ya soon. Thanks for the loan though.
Posted By: savoy64
Re: Alternative prop. valve plumbing "?" - 12/02/11 07:12 PM
think you will need the proper residual valve for the drum brakes along with the prop valve---the residual is set at about 12" column pressure---this keeps your shoes in close proximity to the drums so that you dont have to pump up your brakes everytime you stop----if you look at a hot rod buildup in a speedway catalog you will see you need 2" column pressure on the front discs-------so if you have a rod with a frame mounted master--you have to have a residual for the front(2") and rear(12")----however if you have a firewall mounted master there is sufficient column pressure for discs but not for the drums hence you need the residual valve and that is the forgotten value of the distribution valve...
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 12/02/11 10:14 PM
Quote:
think you will need the proper residual valve for the drum brakes along with the prop valve---the residual is set at about 12" column pressure---this keeps your shoes in close proximity to the drums so that you dont have to pump up your brakes everytime you stop
Not saying I do or don't need it, but I've never had this in the past ever since I've owned the car. It always stopped just fine (well, fine for a 40 year old car). Is their any pics, or a place I can see what this looks like?
Thanks.
Posted By: bigblock340power
Re: Alternative prop. valve plumbing "?" - 12/02/11 11:33 PM
Just got back from a drive in the Duster. Oh, I feel good now! Stopped just fine, I think I did something right (no leakes either). Jumped on it a little, damn nice feeling. Right away I got a few thumbs up (at least I hope it was thumbs). Stopped in the gas station for a bit of go juice. Two guys came over from the other island and said they remembered a Duster like this one a few years ago. I told them this it, I've had it in the garage being redone. All in all a good outing. Now I just need to get that dang 'ol grill done.
Posted By: savoy64
Re: Alternative prop. valve plumbing "?" - 12/03/11 01:10 AM
the residual valve is part of the brass block you are talking about that everyone calls the prop valve/line splitter---and everyone forgets it has another very important function-