Justin 87 GTA

iTrader: (3)

First off, I searched for about 1 hour and came up with this list:prop valves now.(All GM P/Ns FYI..)

82-85.....................14075706
82-83 RR Disc.............25511944
82-83 EXC RR Disc.........25515423
84-85 EXC RR Disc.........25517738
84 RR Disc................25517739
84-85 JE1.................25517740
85 RR Disc J65............25521985
86-88 J50.................14089495
86-87 JE1.................14089496
86-88 J65.................14089497
89 J50 2ND Design.........10136839
89 J65,1LE 2ND Design.....10136840
89 J65 EXC Y82,1LE 2ND Des.10136841
89 J50 1ST Des.............14089495
89 J65 EXC 20TH Ann Y82,1LE 1ST Des..14089497
90 J41,J42................10136839
90 J65,1LE................10136840
90 J65(EXC 1LE)...........10136841
91 Cast Iron Brk Sys J41
Alum Brk Sys J42.......10136839
91 J65 4 Wh. Disc ........10164112

I don't see how this list applies, becaues the only number on the prop that i have is NC 34 KH 18 9, and furthermore, if i get a prop from an 89 car, there are many choices, so which one do I need?
Anyway, here are the details of my setup:i have an 87 gta which originally had a drum rear. I put in an austrailian 9 rear with disc. Like everyone else the rear brakes suck. They don't stop on the emissions dyno....the rear wheels just keep spinning, unless you stand on the brakes, and then it barely stops. I think the autrailian rear is an '89, but i am not sure. What do you suggest? It seems as if I should change the prop, but I am not sure which one to get. An adjustable or a prop for an 89 disc car. Can anyone steer me in the right direction? I read about the prop mod where you put a 5/8" plug in there, but I am afraid that could cause the rears to lock and cause an accident. Which prop valve should I get? what part #. I have a prop in the garage that someone said was for an 89 rear disc car. It is Part # NC 34 KH 18 9. Will this work better than the stock '87 disc/drum one that I have now? Will the adjustable prop bolt right in? Which adjustable one should I get? Will it throw codes? Is it easier to get the correct GM prop for that year? What part number would that be? I'd really liek to keep it simple and put in the correct prop, if I can get it. thanks

Apeiron

The size of the brake lines changed in mid-year 1989, so there are a first design, and a second design. You'd need the first design 89 prop valve (14089497) to fit the lines on your 87. This is the same prop valve used on rear disc cars from 86 to 88.

Justin 87 GTA

iTrader: (3)

so you are saying that prop valve will work on my '87 with an 89 rear? also, will it make my rear brakes stop better? The following number was on the prop that I bought...i was told it was for an 89 4 wheel disc: NC 34 KH 18 9. I don't see any numbers that look like the part numbers you mentioned. Where are those part numbers located? thanks

Chickenman35

Just heave the stock proportioning valve as far as you can throw it and put in an adjustable one. WilWood is one supplier. No codes will be shown. Your car will stop much better. For Non-ABS cars, GM ( and most major mfgs ) bias the front brakes heavily to the front. This is considered " Safe" by little old Granny's and old men ....and the litigation happy society in the US. Of course the car doesn't STOP as well as it could with the rear brakes. But that's the price we pay today to be " protected" from our own idiocy.

Tech article on how to install available right here at TGO. How to install a WilWood proportioning valve

km7152

hmm interesting, i didnt know there were different size brake lines. So if im putting and 87 rear in my 91... I will need the newer style proportiong valve? What about the connections at the rear, those should be fine since the line runs into a brake hose, which t's off the rear...or am i wrong?

Justin 87 GTA

iTrader: (3)

It look slike I have three options:
1- I can put in an aftermarket valve, but I think that making the flares will be difficult and I am not sure i have the time. I am leaning away from doing this, since the next two options seem easier.
2- I can do the 5/8" plug mod, where you thread in a new 5/8" plug into the stock prop valve. My question is how far do you thread it in, and is that how you adjust pressure to the rears? How does that mod really work.
3- I can try putting in the prop valve that I bought, that is supposed to be from an 89, but how do i know for sure that it's the right prop. There is no model number on the prop itself. where do i find the part number on it? I see the master cyl part number but not the prop part number.
thanks!

L.I.N.Y.92CAMARO

If you do number 2 make sure you can do it on your car. I just went to do it and theres a brake line coming from the plug you would normally take out???
So just make sure you car doesnt have a line coming from it.

Justin 87 GTA

iTrader: (3)

and it says something about if you have PBR calipers, you shouldn't for some reason. wonder why? I think choice 1 is out, looks like 2 might be out too. Does anyone know how to find the model # on a pro so I can do #3? thanks

Also, Apeiron...do i need the 495, or 497? thanks

Apeiron

497 to fit the hardlines on the car.

Justin 87 GTA

iTrader: (3)

Apeiron, now I get it...The 495 is for 87 and '89 cars with drums i guess. The 497 will fit my lines, and is for disc so it'll work with my 89 disc rear.....thanks...how do you find the part number on the prop? where is it located? thanks -justin
LINY92 Camaro..if i don't have PBR calipers, and i go with choice # 2, My question is how far do you thread it in, and is that how you adjust pressure to the rears? How does that mod really work.
thanks -J

Apeiron

I don't believe there is a part number on the prop valve. Usually there are only part numbers on things that use a unique casting. Several different prop valves are built from the same housing though.

JB22

OK, I am having a hard time making heads or tails on this.

I have an 88 Iroc that had Rear Disks. I bought a 91Z rear that had PBR disks, and I got the Prop Valve that went with that.

What do I need to do to make this work? Will the lines on my car match up to the 91 prop or are they different size fittings? Do I just have to get the correct adapters to put it together?

Could use some input on this, cant quite get my thick skull around it.

Thanks in advance for some advice.

di11avou

iTrader: (1)

If I understand this mod correctly, you are simply removing the piston and spring that regulate rear brake pressure. The plug is just that...a plug to seal off the passage. It wouldn't matter how far in or out it is and there would be no adjustability.

Allowing full pressure to the rear brakes doesn't sound like a very smart thing to do and could cause you to 'fishtail' or spin out in a panic stop.

MurcoRS

That "tech-tip" needs to go out the window!
If you set your system up like that you'll also limit the amount of front brake pressure...

Chickenman35

What on earth are you talking about? You do NOT limit the front brake pressure at all by installing a WilWood ( or any other brand ) of adjustable brake proportioning valve.

Stock proportioning valve is removed and WilWood valve controls pressure to the rear brakes, which, depending on valve used, can adjust any where from 50% of line pressure to 100% of line pressure....TO THE REAR BRAKES.
Front line pressure is NOT affected at all.

If you don't understand how something works, please ask. Don't post mis-information. THOUSANDS of Road Racers and Autocrossers modify their vehicles this way....and they don't have any problems!!!

MurcoRS

Ok, I asked several members of the Bendix brake engineering staff during a training seminar last year and they each had SCCA, NASCAR, or Indy car backgrounds and each blasted the set-up shown in the tech article. An OEM master cylinder has two chambers that act together to develop pressure for the brake system, correct? If you limit the amount of pressure in one chamber (what a prop valve does) the piston for the front primary chamber does not continue to advance independent of the rear primary chamber therefore limiting the maximum pressure developed. As far as racers go, they will run independent dual masters when allowed and if not allowed they will run the set-up recommended by Baer - disabling the OEM rear prop in the combo-valve and running a prop downstream in the circuit. Also, they eliminate any variables such as weight distribution, tire type and size, chassis set-up, etc. and set the adjustable prop valve pressure limit right on the fine line (and it's a very fine line) between front and rear lock-up. This requires extensive maintenance (like any competitive racing) and is completely impractical on a street driven car and can be downright dangerous.
Also, I guarantee anyone running the set-up in the tech article for more than 20K miles on the street has torn-up some rear brakes and has little front brake wear.
If you cap the pressure to the rear lines with no way to send excess pressure to the fronts (what a combo valve does) you limit overall system pressure in direct proportion to the rear pressure.
Just because somebody posts something YOU don't understand, don't assume they are misleading people...

Chickenman35

Now I usually don't like to flame people, but with due respect....I'm sorry fella...But you just have it all totally, totally wrong.


It is rather plain to see that you don't fully understand what is going on and don't have even a basic understanding of how a Tandem Hydraulic Master Cylinder works.

As far as your claim that all these "engineers" all had Nascar, SCCA or Indy Car backgrounds...that may or may not be. (Personally I think you're name dropping to try and impress). Mind you, I've been to lots of seminars in my 30 YEARS of racing , with " so called" experts who have offerred the most ridiculous advice. Turns out most of these " experts" turn out to be Salesman who don't have a clue what they are talking about. Any one with any SCCA experience knows that there are THOUSANDS....lets repeat that THOUSANDS... of amatuer racers running WilWood style proportining valve on Tandem Cylinders with no problems what so ever. To deny that is just ridiculous.

Now to a Nascar or Champ car engineer.... NO a hydraulic proportioning valve is not the IDEAL way to limit brake bias....BUT, it is perfectly acceptable.

Don't take my word for it. Phone WiLWood, or Tilton or how about this little bitty company...... General Motors. GM used an adjustable Kelsey Hayes on the Corvette back in the early Sixties and Seventies. Do you honestly think that GM doesn't know what they are doing.

You're totally wrong with your Master cylinder scenario. You really don't understand how these things work do you? Please go buy some books and find out how basic systems work: A good starter is:

Brake Systems: OEM & Racing Brake Technology

Brake Systems: OEM & Racing Brake Technology

Read through it to understand how a Hydraulic proportioning valve works. You've got a few mis-understandings.

1: Installing an Adjustable proportioning valve as described in the Tech article does not affect line pressure your front brakes AT ALL!!! You always receive 100% line pressure to the front brakes, with a factory valve or an adjustable one. The factory valve works EXACTLY the same as an adjustable valve...except it has a preset curve.

2: The pressures INSIDE the Master Cylinders are not affected at all by ANY type of proportioning valve added to the rear line. You could totally plug the port to the rear brakes and you would still receive full braking to the front barkes. A proportioning valve, be it Factory or Adjsutable is a "restrictor"

It simply restricts the fluid volume going to the rear brakes. Unless you have a leak...the Pressures INSIDE the Master cylinder remain constant. Sometimes this is hard to understand....but it is covered in the first week of any " Hydraulics " Technical schooling.


Really???...post a link. All that Baer says in their online Tech guide is that an Adjsutable valve in installed in the rear line. Me thinks you read " something" " some where" and just didn't understand it.

BTW, you cannot just " gut a stock proportioning valveand try and use it as a Tee fitting. Bad, bad things will happen....such as pumping all the fluid from the Primary Reservoir into the Secondary Reservoir. You also cannot use the Stock Proportioning valve in conjunction ( series ) with a Adjustable unit. You will end up with a very long pedal if you do that.

Baer Brake Systems FAQ1

Baer Brake Systems FAQ2

Well...it's plain to see that you've NEVER even tried this mod...... or if you did , completely screwed it up. An absolutely ridiculous claim. Just utter BS.

You GUARANTEE that someone running the Tech article setup will have torn up rear brakes and have little front brake wear. Why do they think its ADJUSTABLE? You can put as much rear brake bias as you want to the rear brakes. Even less than the Factory....if you're that inclined. Lord what a stoooopid comment to make. BTW...I've got $1,000 bill sitting hre that says I have at least six competitors that I can ring up in 30 minutes, that have over 40K on their Street driven Autocross cars, using adjustable proportioning valves. NO unusual pad or rotor wear.


Impractical on a street car? You're joking right? How is it impratical? Is having better braking capability impractical? You've got guys on this board, such as myself, Dean, Dewey316 ( and dozens of others ) who have run these things for years...ON THE STREET... with ZERO problems. I've had the Camaro for 8 years with an adjustable valve

Are you just making things up as you go along? You do realise that our cars ( 1st through 2nd GEN) did not come with ABS? You do realise that the Factory PV has no " automatic adjustment of ANY sort for varying loads or road conditions? That makes it no better than an adjsutable valve...and in most cases a lot worse.

Maintainence????? There is no freakin' maintainence. How often do you maintain your kitchen faucet? A proportioning valve, whether factory or after market is about as simple as it gets.

Have you actually read any of the multitude of posts on the brake board with people complaining of little or no rear brakes. Nine times out of ten it's because the Factory PV has gone "Tit's Up". An Adjustable unit is even simpler than the Factory one.

"Downright Dangerous"...Well...only if you're an idiot and crank in TOO much rear bias. But " most" of us here are enthusiasts and do actually know how to " tune " things. Including Suspensions, barkes and Engines. Wait...I've got it figured out....you're really Ralph Nader!!!


That is NOT what a combo valve does...NOT IN ANY WAY SHAPE OR FORM!!!. Read some books and get some knowledge before wasting any more time with your fiction. Sorry if I'm being harsh....but you'r posting Crappola. Get some books, read them and get some knowledge before posting back. Maybe get some real racing experience (Road Racing..if you want to talk about brakes and not get thrashed ) as well. You've got about 30 years of racing experience to catch up to me and most of my competitors.

Sorry...but I'm not going to waste any more of ny time on this. If you want to learn something, go buy the book I recommended. and have a re-think on what you've said. You're wayyy off base on this. regards.

MurcoRS

Let me back-up a little as I was writing at 11 at night... The front brakes will show excessive damage from lack of a metering valve... done
Ok, everybody else step back and let me shoot this down once and for all. I've never flamed anyone on this board as well and I don't intend on making my point by doing it here either but by proving it to you...
The guys I spoke with were most definitely not salespeople, they were engineers with very little people skills. 20 years of dealing with those types makes them easily recognizable. I too thought this was the "hot set-up" just as you do until I had these conversations last October when I pulled-up our website tech section and showed them what I had planned to do on my car.
I'll prove my point, as it was proven to me...
* Take a new OEM-style master cylinder and bench-bleed it. Then cap-off either of the two outlets and see what happens when you try to pump fluid through again. If you restrict the output of one you do so with the other as well. What happens to many who do this modification is they damage their master cylinder and create an internal bypass in the forward primary chamber. Take one off of a car that has run this set-up for some time, it's bypassing...
* If you indeed have your brakes plumbed this way and have it adjusted in the manner described try this... Find a large, OLD, empty parking lot with a friend and have him watch as you try to get all 4 wheels to lock-up from 40-50 mph, they probably will. Try this again on a freshly paved parking lot, they won't. Now, I don't know where you live but the roads I drive every day have varying surfaces and each of them will change in surface friction during every day based on time, teperature, moisture level, surface contaminates, etc... How can you possibly adjust one of these units to provide a SAFE bias for all of these varying surfaces?
* If you are racing competitively and consistently you hopefully have your car scienced-out and have eliminated any variables such as weight, balance, and traction. How can you adjust anything on a race car without starting from the same point consistently? Now, how often do you drive on the street with varying loads (gas, passengers, gear)? Do you jump out and adjust your bias when you load the car up? How about when you change tires, pads, or stereo equipment?
* A factory combination valve has a metering valve to provide balanced braking front-to-rear, a pressure failure warning, and a safe proportioning valve that functions as a comprimise under most any road surface from perfectly flat and grippy to snow covered. If you blow a hose with the set-up shown in the tech article you won't know it until you have your foot go to the floor after most of the fluid has left the system. If you drive on the street you must make these comprimises. Fortunately for us GM blessed the 3rd generation f-body with a bolt-in combo valve that offers the HIGHEST REAR BIAS OF ANY ANY FACTORY COMBO VALVE EVER BUILT (the 1LE combo valve) and it comes in 2 flavors for different line sizes, has a pressure-loss warning, and a metering valve. Use one of them with pretty much any rear OEM brake set-up you can imagine (1LE, LS1, C5&6) and you will be safe as all of them have pretty close piston volumes.
If you back-down your rear bias on your adjustable unit to account for variable street conditions how far do you go? Do you have line pressure gauges on your car? Do you routinely run friction tests on your ocal roads? Where is the line between "phenominal braking" and safe street use? You could back it down further than a factory combo valve and not even know it. Then, what's the point of making this modification on a street car, losing the combo-valve's safety features, and potentially damaging other components? I'd rather GM's lawyers prove their set-up in a court of law than my own lawyer trying to prove my home-spun modification was sound. Brakes are the #1 safety feature of any car and I'm not willing to risk my safety, and others, by putting something on my street car that was designed for a race car that could affect my ability to operate it safely. I draw a very distinct line between race cars and street cars as anyone who has driven both does. If I put a 600 hp engine in my street car and don't get something right it probably won't kill anybody. If you screw-up something in your brake system and your running autocross you'll probably just spin-out while trail-braking into a turn, no harm done. I'm no Ralph Nader and I would have torn his arguments about the Corvair to pieces in court but you have to be safe with modifications to your street car.
If you insist on running the tech article set-up in your own car, fine. I will err on the side of comprimise in the name of safety everytime for myself and others, especially when discussing modifications and the audience has people of varying degrees of skill and experience. As long as you aren't driving in my neighborhood with this set-up I could care less. However, If someone ever hit me in a car set-up with something like that I would own their a$$ in the courtroom!
----------
GM has NEVER put a user-adjustable brake bias valve on any street car, ever.

Chickenman35

Sigh.....Ok I'm going to take one more crack at this. You've NEVER run this on your car. You state that very clearly. You base all your arguements on your own theories... which are being made up as you go and are based on half baked assumptions.ed answering several rather pointed questions which shot down your arguements.

I'm 52 years old. I've been Road Racing, Rallying, Ice Racing, Hillclimbing and Autocrossing for 30 years. I crew on a 185mph GT1 racing car. I've won several National Autocross titles and hold the records at several Hillclimbs and tracks. I've lost count of how many Engineers and Professional crew chiefs I've hung out with over the years. So I do know a little bit about Autocross\racing and running dual purpose cars.

#1: Statement wrong . You state that: "GM has NEVER put a user-adjustable brake bias valve on any street car, ever." Hate to burst your bubble....but GM did use an adjustable unit as I stated on Early Corvettes ( Mid 60's as it turns out ). It was a Kelsey-Hayes Unit and was the grand daddy of what all modern adjustable proportioning valves use. Page 171 of " How to make your car handle" By Fred Puhn ( A must have in any Autocross\Road Racers ) shows the old beast. Now I'm not going to look all over the Internet for the original Factory GM number ( because they are rare ) but GM did produce these. Any one who knows anything about early Corvettes knows this....it is an indisputable fact.

#2: Arguement wrong. You go through great lenghts about differing road conditions, wet, dry, bumpy, smooth, more weight less weight etc.... with the assumption that the Factory PV corrects for thes conditions. IT DOES NOT!! The GM Factory PV ( supplied on our cars ) is a very simple device. It is a very simple spring loaded proportioning valve that has a PRE-SET bias curve based on brake pedal pressure. It cannot adjust to ANY different road conditions, be it wet..dry bumpy or smooth. You imply or think that the Factory PV takes all these things into account and automatically changes the brake bias accordingly. REPEAT.... IT DOES NOT. You're fooling yourself if you think it does. So in that respect it is no different than an adjustable unit...in fact it ( Factory PV ) is worse because:

A: The factory errs on the side of caution and puts a very large bias to the front brakes. Lawyer types and the general un-educated drivers think it is "safer" to lock up the front brakes and plow into the car in front... rather than having the car actually stop faster if all of the brakes work at their full potential. To actually make all 4 wheels brake effectively and adapt to changing conditions ( road surface and weight ) takes ABS. ABS is expensive, so GM cheaped out and put a very simple...but very dumb ( in comparison to ABS ) hydaulic proportioning valve on our cars. BTW...European spec cars typically have a much higher rear brake bias than North American spec cars specifically because of DUMB-*** North American drivers and the USA's litigation happy society.

B: With an adjustable unit you can actually can change the brake bias "curve" for different conditions. For racing you can mount it in the **** pit and adjust for different conditions. IE: If it rains or you burn off fuel.

For the street...you set it... and forget it. Now that takes a bit of skill. You have to err on the side of caution....just like the factory does, and put a bit more bias to the front. But the Factory waayyyy over does it for an experienced driver. An experienced driver does NOT slam on the brakes in the middle of the corner. Stooopid people do..and GM has to cover their asses because these same STOOPID people go running to their damned Stooopid Lawyers at the drop of a hat. So we end up with **** poor rear braking. ( Note the number of complaints about poor rear brakes on this board!! )

BTW...bringing up crying to your Lawyer to make your point is really a bad call MurcoRS. I can't believe you actually said that....

C: Now you're just making up stuff. Wheres your proof? Do you have the design specs? From experience...cars with J65 spec brakes will actually out stop a 1LE car on the street and in Autocrosses. 1LE cars are infamous for having too much front brake bias. They get better at the track, but for street use they have way too much front bias. BTW, I have 3 friends with 1LE's and and 1 with a rare LB9 ( Cop - Spec ). All had inferior braking on the street to J65 cars. Do some research on this board. Most drum brake cars stop better than 1LE cars....until you modify or replace the proportioning valve. This is all real life experience from running these cars ( 3rd Gens ) in National Autocross competitions for 10 years.

Chickenman35

3: Do you really understand how an adjustable proportioning valve works? And for that matter a regular Factory PV?

A really good site to properly understand the " Basics" is " How stuff works". Read a little on your combo valve.

Howstuffworks "How Master Cylinders and Combination Valves Work"

A factory PV is a very simple, spring loaded valve that limits the amount of pressure to the rear brakes according to front line pressure. At low pedal pressures the front and rear brakes will receive nearly identical pressures as weight tranfer,front to rear, is minimal. As the braking increases, front line pressure goes up in a linear curve, but the back pressure does not go up in a linera curve. As braking pedal pressure ( Front line pressure ) goes up. the difference between front and rear barke pressure curves increases....necessary because of weight transfer to the front wheels. The spring inside the Factory PV controls the Bias curve. There is a preset limit at a " Cut off point" that restricts maximum rear line pressure.

Here is an example of a factory PV brake pressure curve. Actual numbers are for illustration purposed only. But this is how a PV works.

Example A:
Very light braking: Front Line Pressurre 50 psi \Rear Line Pressure 50 psi
Light braking: FLP 100 psi \ RLPpressure 95psi.
Moderate braking: FLP 250psi \ RLP 175psi
Moderate heavy braking: FLP 500 psi \ RLP 300psi
Heavy Braking: FLP 1000psi \ RLP 700
Panic stop: FLP 2000psi \ RLP 1000 psi

Note the " Cut off " point...in this case 1000psi. That is a preset limit based on spring selection and orifice size. Both Factory PV's and afternarket APV's have an upper " cut off " point. When you buy an APV, the limits brake pressure curve is usually in the instructions.

Now an adjustable valve operates in the EXACT same manner. It is spring loaded just like the factory unit. So the brake bias curve is not linear....just like the factory curve. I think this is what many people mis-understand about adjustable PV's. Most people think that they have brake curve that is linear because they think you adjust a tapered needle. That is not how they work.
With an APV, what you adjsut is the pre-load on the spring inside the unit. So just like a Factory PV they have a pre-defined barke pressure curve designed by engineers. By changing the tension on the pre-load spring, you can move the lower, mid and ( to a certain extent ) the upper pressure range.

So taking the same car and putting in an APV we could end up with a brake bias curve like this. Lets assume the car kept locking up the front brakes pre-maturely...a common problem with our cars.

Example B:
Very light braking: Front Line Pressurre 50 psi \Rear Line Pressure 50 psi
Light braking: FLP 100 psi \ RLPpressure 100psi.
Moderate braking: FLP 250psi \ RLP 225si
Moderate heavy braking: FLP 500 psi \ RLP 350psi
Heavy Braking: FLP 1000psi \ RLP 750
Panic stop: FLP 2000psi \ RLP 1000 psi


Note that most of the adjustment is in the low to mid-range. The upper range on an APV (at maximum adjsutment) is usually higher than a Factory PV...because these units are used for racing. Race cars usually have a lower CG and less front to rear weight transfer.

Note that with an APV you could also set up the brake pressures with less bias than a Factory unit.

Through out this...remember that a Factory PV is a " dumb" device. It is set to ONE PREDEFINED BIAS CURVE THAT CANNOT BE CHANGED ( unless you rip it apart )....and does not change according to road or load conditions ( exception being some variable PV for pickup trucks that do change with load....but our cars don't have those ). An Adjustable PV has a BIAS Curve in which the Lower and Upper limits can be changed. That is the only difference between the two...as far as brake proportioning goes.

4:Metering valve in the Factory Combination valve is only used with rear drums barkes. 4 wheel disc brakes cars do not use the metering valve. With drum brake cars a simple residual pressure valve will achieve the same function as the factory metering valve.

Brake failure warning lite is the ONLY thing that you lose when doing the mod. But have you ever actually EXPERIENCED a catostrophic brake failure? I have..in a Production car with Factory combination valve ( racing situation ). The stoopid little warning light is the LAST thing you'll notice...as your floor goes IMMEDIATELY to the floor!!!! If you blow a piston seal, brake hose or anything else the Factory Combination Valve on our CARS does NOTHING...REPEAT... NOTHING different than one with an Aftermarket PV....other than turning on the stoopid little light....Which you may notice after you're picking yourself out of the back of a dump truck.

Proportioning valve features? Well we've already covered that. Yes it's a safe comprimise. So safe that it COMPRIMISES the cars braking capabilty to keep GM "safe" from Lawyers due to idiot drivers.

A factory PV is one of the WORST things to have in the Snow. Remember... A FACTORY PV CANNOT COMPENSATE FOR ROAD CONDITIONS....you have no weight transfer in snow. Now most of us are not going to drive our babies in the snow...so it's kind of a mute point. But I live in the Vancouver BC area...also known as the Wet Coast. It rains here ALL the time. Wet roads do call for more rear brake bias than dry roads. Less front weight transfer. I adjust my WilWood PV to give maximum braking in the wet. Fronts lock just before the rears in a " Panic" stop. Maximum braking. Factory PV setup cannot stop anywhere near as fast. I know...I've had both setups on the car when it had J65 brakes.

For street driving in the dry, I will generally just leave things alone ( On the wet setup) as it is fairly close to maximum braking. When I autocross or have Track Days I will usually crank in another to the front ( Technically 1 turn LESS to the rear as front line pressure is NEVER regulated...even by Factory Combo Valves ). You simply cannot do this with a Factory valve. As you state...a Factory valve IS a comprimise....and it can be improved on.

5: You do NOT lose any of the safety features that a Factory Tandem Master cylinder provides in case of a brake failure such as a burst hose or blown piston seal, when you install an aftermarket APV. The Tandem Master Cylinder will work exactly as it is suppossed to with the APV. A factory Combo valve does not control any safet features in the case of a blown hose etc. All of that is controlled by the Mater Cylinder design. The only thing a combination valve does that is different in a Catostrophic failure scenario...is to turn on the little warning lite.....and when that comes on it's too late Charlie!!

Read up some more on how Tandem Master Cylinders work. It's pretty basic, but factual. The moving diagrams are quite good:

Howstuffworks "How Master Cylinders and Combination Valves Work"

I'm really sorry MurcoRs...but you're just posting absolute drivel. What are you trying to prove? You don't even seem to understand the basics of how Modern Tandem Cylinder works and the forces involved.

When bench bleeding, with open ports feeding back into the reservoirs you can barely compress the secondary spring. By blocking a port you dead headed the system. Fluid is not compressable ( air is...that's why you have to bleed as brake system ).

A modern brake system can, with your average NA male, can generate up to 2,000 psi in a panic stop or 1,000 psi in a fairly hard stop. A common brake pedal ratio is 6 to 1 ( manual brakes ). That means 333 lbs of force during a Panic Stop and about 166 during a fairly hard stop. Now thats' a lot of force...and our fairer sex generally cannot create that much pedal pressure. And so Power brakes were developed. Now you'r trying to recreate some sort of pressure test on a Bench by blocking the ports? With a 1" piston, no mechanical advantage and no Power boost, you'll be lucky to generate 150psi of system pressure. What is that going to tell you? Frankly I don't understand what you're trying to prove.

You say the Master Cylinder will bypass if you restrict one of the ports? That's exactly what a Factory Proportioning valve does. You're making BS up as you go.

Really? You're sure about that are you? No I don't think so...you're just making up more half baked theories to try and support your rapidly " crash and burning arguements".

Where is you proof??? These units are used by THOUSANDs of enthusiasts who drive their cars on the street and compete in AutoCross or Track Days with virtually ZERO failures. Don't you think you'd read about failing Master Cylinders and other problems with all of the field testing going on? Don't you think it would be front page news on every Road Racing or Autocross forum out there. Why isn't it?? Because you're wrong

I've been Road Racing and Auto Crossing for 30 freakin' years. I have yet to come across or even hear of ANYONE damaging a Master Cylinder in the way you describe.

If you think about it logically you will understand why. Factory PV 's and APV work on EXCATLY the same principle!!! If you can't understand that then please don't waste our time with your **** and bull theorirs. Sorry if I'm getting nasty... but I've wasted a lot ogf my valuable time having to debunk a lot of the mis-information that you have posted.

There is one thing that I will agree with you on:

I will agree that this modification is not for the Novice. But this IS an enthusiasts board and with that goes the caveat that you should know what you're doing.

Your last sentence though exactly illustrates the problem our society and our litigation happy USA...and why things like Medical Coverage ( and a HOT cup of Mcdonald's coffee ) are so hard freakin' to find.

No proof, no evidence.....but "OMG...you've modified your cars brakes. I'm GONNA SUE YOUR A**"

But sadly you are right with that point. Maybe the Tech article should be removed so that 3rd Gen doesn't get sued. I guess the dumb-asses and Lawyers will win again.

PS: Sorry for the long recital all, but it's a rainy day....and I can't work on my car. Lawyer comments really chaffed my A**though....

MurcoRS

You make several excellent points and I'm more than willing to engage in conversation on the topic and appreciate your response. I'm no spring chicken either and have a little bit of background in brake systems from running a brake shop for many years, until April. My "lawyer" arguement simply comes from my experience in running that shop. Fortunately, of the 3 cases I was involved with I won them all and the drivers had made mistakes they were trying to cover for. I look at safety first and am intimately familiar with OEM brakes. I will respectfully disagree with some of your points based on the following
*The limit of my brake modification experience is with creating and installing a LS1/C5 conversion on the front of my neighbor's '88 IROC and converting the rears from drum to an OEM '89 PBR system. In the process I changed the combo over to a 1LE unit, the master cylinder to a new '99 f-body unit, 1LE hoses, and swapped-in the correct parking brake cables. After completing the swap we measured the 60-0 distance using Bendix titanium pads and new Comp T/A KDWS tires and compared them to my '06 Jetta's published numbers and came within 8' of them, repleatedly. I was thrilled and found the pedal to have very linear pressure build-up and extremely good feel, which was also very welcome. I have gathered the components to do this on my own car and will do this very soon.
*In planning for my own swap I consulted the Bendix engineers that spoke at a testing seminar I attended last fall, showed them the tech article and explained to them that I had planned to do this myself. I was told what I wrote in my previous post. If they fed me the wrong information I apologize, but I would expect R&D people who work for the company that invented hydraulic brake systems to be giving pretty solid advise! You obviously have more experience with racing oriented systems and I cannot, and won't argue with that.
*I have had a front hose get cut from road debris and had the warning light come on with plenty of residual pressure to safely stop the car (the noise from the impact also clued me in). I've also had customers lose wheel cylinder seals, burst rusted lines and worn hoses and had enough fluid remain in the system for 1 safe stop - I'm convinced it's a worthwhile safety feature...
*As a teenager in the early 80's I worked for Wayne Walker of Zip Corvette Restoration center in Mechanicsville, VA assembling and detailing restored frames. Many, many mid-year Corvette frames went through there including the rare L88 and Z06 cars and none that I ever saw had an APV. Could this have been a dealer-installed option?
*The statement "the 1LE prop-valve has the highest rear bias ever offered by GM on a street car" was taken directly from the last article reprinted in "The best of HOT ROD - Camaro performance 1989-1996"
Amazon.com: Camaro Performance 1989-1996 (Hod Rod Magazine Series): Books: Best of Hot Rod Magazine The article was for the then-new 1989 IROC-Z 350 and it specifically said that. Once again, going on the most authoritative source I'm aware of...
*At no point did I say that a factory prop-valve adjusted for anything. I'm fully aware that it has a fixed maximum pressure value and the point I was trying to make is if you back-off an APV to compensate for varying street-driven conditions it's of little value on a car that is 99.999% street driven, and not worth the loss of a worthwhile safety feature. BTW - every GM 4-wheel disc car does in fact have a metering valve and I've disassembled and cleaned my fair share of them. They are usually set for 2-4 psi and I've attached a pic of the one in my 1LE prop valve.
Yes, we do live in a litigious society and I've had the legal hammer pointed at me more than once so I am keenly aware of how silly it can get. However, it is our reality and if some numb-nuts cobbled-up something unsafe in their brake or steering systems and hit me because of it failing, God help them!
I have worked on and successfully fixed literally hundreds of brake systems and even with that background I can still be humbled on occasion.
Your posts were very informative and I learned from them. I look at being proven incorrect as a learning experience and I hope others on this board will do the same.

Chickenman35

And I do appologise if I sounded a bit harsh. I'm recovering from surgery for appendicitis and have been a bit "testy" the last few days. A good discussion all around and once again, I apologise if I was too harsh.

Richard

PS: It's sometimes hard to converse over the Internet when you don't really "know" the other person. And its' very hard to convey meaning and expressions. I sometimes feel that we are very lucky that Kennedy and Kruschev did not have e-mail back during the " Bay of Pigs ". Otherwise the Earth would still be a great, molten glowing crater.....

vissrx7

Hey guys -



Thought I'd share my experiences with installing the Baer 1LE front brake setup on my 1992 Z28. The car was bone stock, and came with the PBR rear calipers from he factory and the single piston cast iron calipers on the front.



1. I kept the stock Master cylinder and Proportioning (combination) valve. The car has 89000 miles, so I am not sure how good the MC is internally. I disected the prop valve, and everything looks good in there though.


2. I have bled and bled the system, but I still seem to be experiencing a leftward pull under hard braking. It doesn’t seem to yank the wheel from my hands, so I assume it’s probably the right rear brake not working 100%.

3. Under medium-hard braking, there is a clicking noise from the front left it seems. It clicks about once every tire revolution or so. I am not sure what it is so far, but I checked the tie rods and ball joints and they seem good. Might be the tire rubbing the fender well actually. I have to measure the difference in offset from the old brakes to the new ones – the new ones definitely put the front wheels further out. I have the slotted rotors - not sure if any noise might be coming from a little burr or something on there until it wears down.

4. Before the install, it had a perfect front end alignment, but since I had to put on the new spindles with the Baer kit, it probably (definitely) needs an alignment – which may or may not have something to do with #2.


5. It stops great, but I haven't locked up the brakes (any of them)…I haven’t totally blasted the brakes yet, so I guess I’ll find out soon enough if the rears or the fronts lock up first. As far as balance goes, it actually feels pretty balanced – obviously, I am not sure how close or far I am from optimum performance.

The biggest difference is that the pedal feels MUCH more firm. Less travel, and "mush" than stock, even with new stock brakes and a good bleeding job before the swap.



I ran some calcs based on the piston size of the Baer brakes vs the stock single pistons - compared to the sh*tty stockers, the Bears actually have much less piston area on which the brake fluid pressure is acting on, so from that respect, with no other changes, the brake forces will automatically be biased toward the rear more than the factory setup (less piston area = less brake force for a given line pressure). However, the increase in rotor size with the Baer kit somewhat offsets this fact, as does the increased front pad/caliper rigidity. Just on the piston area and the rotor size increase (not factoring in the rotor stiffness increase), the bias to the rears should be about 25% more than with the stock front brakes. I am not sure how to quantify the stiffness increase...

trumps2000

iTrader: (2)

vissrx7:

When you say you dissected the prop valve, do you mean you removed the spring and valve and installed a plug?

I think you have a very similar setup to what I'm building. I have an '85 with iron calipers in the rear and I'm installing C4 12" brakes up front. I wanted to install the adj. prop valve, but I bought S/S lines and they're a huge pain to cut and flare, so I'll save that for someone with the tools. I also went and replaced the GM prop valve with a plug.

Chickenman35:

How exactly does the prop vlave work inside that makes the plug not such a great idea? I would prefer this method to keep the idiot light and to make the installation cleaner.

I noticed I had some trouble bleeding the rears. Fluid wouldn't come out until I backed off the plug a little then it bled fine. Also the spring I removed had a little surface rust on it. I guess from sitting empty for the number of years it sat, but is it something to worry about?

vissrx7

trumps2000 - sorry, I should have been more specific - when I said that I dissected the prop valve, I meant that I opened it up and took a look inside. I then cleaned it out, put it back together, and put it back on the car.

If you remove the spring and plunger and put a plug in the end of the prop valve, you will have no rear proportioning at all, I believe. You'll need rear proportioning, so an inline adjustable pop valve could be installed downstream, perhaps... That is, unless you like "drifting" the rear wheels!

For the idiot light, you can actually just unplug the low pressure switch and the light won't be on!

To be honest, the method by which the combination valve proportions the pressure to the rear is a bit mysterious to me. Upon opening it up, I was expecting to see it functioning a bit differently. Here's how I'd describe it:

The front of the prop valve has a fitting with a rubber nipple over it. If you remove the rubber nipple, and look through the hole, you would actually be looking at the back of a plunger. If you remove the fitting from the prop valve, you'll see a spring that pushes the plunger into its bore. the plunger has a weird looking serrated shaft seal. Oddly enough, the spring seems to be uninvolved with the actual proportional constant of the pressure regulation - that is, the spring seems to set the initial breakpoint in the proportioning curve, then additional fluid pressure entering the prop valve from the MC causes the shaft seal on the piston to deform, thereby limiting pressure to the rear brake port. All of this functionality applies solely to the rear brake ports only. The front brake ports are not involved.

I think I lost myself with that explanation! Does anyone know if I am correct with this explanation, or if my understanding is completely wrong??

As for the setup you're planning, are you keeping the iron rear caipers? if so, you may want to look into their piston size in relation to the later PBR rear calipers. It may lead you in the right direction as far as the right prop valve to use...if you decide to put a stocker back on there.

And for everyone's info, I know a guy who used to work at the shop that "created" the 1LE package so-to-speak. I forget what it was called...I am sure one of you knows (something like "prototype automotive fabrications"). At any rate, on the subject of the front brake conversion on 1LE cars, he remembers an engineer being present from Bendix during the brake calibration procedure. He had a parts tray with different springs and (I believe) different plungers for the prop valve.

BOSS 357

iTrader: (1)

I'm trying to determine which prop valve my 89 Formula J65 has before I convert to 1LE brakes. My car was probably built around 5/1/89, would that make my car a "late 89" car? (as it relates to the 2 different prop valve designs) I noticed from the table at the top of the thread that my car either has the 10136840 or 10136841 PV - of which I (think) I need the 10136840 for 1LE. I cannot distinguish the stamping on the side of the PV, so is there any other way for me to pinpoint this part number?

Arrgghhh...
Eric

trumps2000

iTrader: (2)

Here's a link to Dan Burk's page, search down to the section on the combo valve for the info:

How to Upgrade to 1LE brakes

(Off topic) I'm getting 3.73s put in my car, but I can't find new speedo drive gears. Did you change them to correct the speedo? If so where did you get'em?

BOSS 357

iTrader: (1)

Thanks for the reply, but I know all about the part numbers. I was probably wondering if anyone who had a car like mine would know their part number. I'm hoping I can use the existing PV instead of hunting down a new one.

I did not replace the speedo gears. Mainly because no one seems to make the driven (I think) gear anymore. I have the exact info on this at home (at work now) but I would have to have my speedo recalibrated insted. If you find the gears that work for this, there are a bunch of folks out here who'd love to share in that information

Eightyninef

I need to enter this discussion.
my car is a may 1989 build 89 Formula J65 that I BROUGHT NEW. (late 89)
The brakes always sucked from the factory.
so I brought a NEW 1LE brake setup from GM, down to 1LE spindles.
(I left the OEM prop valve in there). The brakes still SUCKED with the 1LE front's, J65 rears. Terrible, terrible, brakes.
Now my C4 with the same pads all around stops great. #412 & #413
So now I started playing with the prop valve.
I got the 2nd design 1LE prop, didn't fit !!!!
so I got the 1st design 1LE prop, and it fit.

1st test drive was in the rain, and my rears were locking up like crazy !!!
Like never before, the rears would lock. So therefore, the 1LE prop is definately rear BIASED.

Next day, stopped raining, roads dried up, and the car stopped much better, and the rears wern't locking up so fast. SO there definately is BIAS problems with the factory 1LE setup. The rears need ABS....

MurcoRS

My one-owner 1989 is also a late '89 (4/89) but the "first design" 1LE prop-valve fit too! I also replaced the master cylinder with a new Bendix unit for a 1999 F-body and it feels terrific! Easy modulation, terrific feel and linear pressure build-up. A bad master would cause the problem you described and even if it isn't bad it's still 17 years old and is past it's prime!

BOSS 357

iTrader: (1)

Hey Murcio & Larry, wanna compare VIN #'s and see how far apart our cars were on the assembly line?

In that listing of part #'s and PV's, I notice all J65 cars had the 1LE prop so if the prop in my car is really J65, I'm safe. But I found the master was switched to the 1LE/drum which leaves me wondering what PV I have. I put this in another thread but I'll ask again here if there is any physical difference or number or marking or anything to help diferenciate between these parts. Most any other part has the 8-digit number stamped somewhere on it but noooo, not the PV's.

Sheesh..
Eric

Eightyninef

The 1LE prop and J65 prop are different.
and now I'm wondering why the TTA prop is totally different.

BOSS 357

iTrader: (1)

Then perhaps you can correct me. According to the chart above for an 89, everytime J65 is listed, 1LE is listed on the same line for that part number. What am I missing?

Eightyninef

trumps2000

iTrader: (2)

Well just to update everybody, a couple of months I finished my brake system rebuild along with everything else to get the car on the road again! This thing now stops on a dime even with the rear iron calipers, so well in fact my buddy was getting car sick while we were bedding the pads and tuning the adj prop valve.

Mods to date:
Front 12" C4 w/ Hawk HPS pads, Earl's lines, all S/S hard lines
Replaced rears with reman iron calipers and raybestos pads
Modified factory prop valve w/ plug, plumbed adj. prop valve in between M/C and factory valve

Pat Hall

iTrader: (31)

Just thought I'd chime in on GM using an adjustable Kelsey-Hayes proportioning valve. One car I know for a fact used them were the 1969 Camaros with the JL8 four-wheel, Corvette style brakes. Since they only made about 200 of these, I don't really know if you could even consider them a "production" car though. I have several old books that have photos and information on the extremely rare options for first gen Camaros, and there's several pictures of the Kelsey-Hayes adjustable valve mounted to a factory bracket next to the master cylinder. In fact, I have one of those rare valves sitting in a box. I happened to snag it on ebay from a guy that was getting rid of a bunch of old NOS GM stuff. In fact, I just grabbed it from the garage, and here's the updated part# that's on the original box (#14084822). I think the reason they updated the part# and still had it available is so that you could order it for any 4-wheel disc equipped GM vehicle to fine tune your brake bias for racing purposes. On the mid-60's Corvettes, this valve was included when the J56 brake package was requested, which was the "performance package" version of the Corvette brakes at the time.

Tremo

Of the stock factory prop valves, which one gives the most bias to the rear brakes? The 1LE or the J65?

Pat Hall

iTrader: (31)

From the posts I've read, the 1LE valve provides the most bias to the rear.

Tremo

Then that begs the question of if the 1LE valve could be put on a J65 car?

Pat Hall

iTrader: (31)

Do you still have the original iron rear calipers on your 88? If so, I know the master cylinder is a different model, but I would think the 1LE p.v. would still work with your system, as long as you get the 1st design valve (GM part#14089496) That valve will have the correct thread size for your 88. I bet EB Miller88 could answer your question for sure. He's pretty much the resident brake system expert here on the boards. Send him a PM.

83 Crossfire TA

iTrader: (2)

FWIW, I talked to a couple of techs over at baer, and they were pretty adamant that you either want to completely gut the rear brake side of the combination valve, or remove the thing completely and run a y block for the front brakes and prop valve in the line going to the back.

I’m curious… some of you seem to be saying that you used a 4th gen MC in the place of a 3rd gen one, do you mean it just bolted in the place of the 3rd gen one with no other changes?

trumps2000

iTrader: (2)

When you say gut the rear section do you mean just the spring and plunger? When I gutted mine I removed the spring and plunger. My car was 4 wheel disk to begin with, so it has no metering. All that was left in there was the idiot light which I kept. I see no reason why that would cause a problem.

83 Crossfire TA

iTrader: (2)

The debate seems to be that removing the thing entirely might cause a problem, which I can’t find a reason for, and apparently Baer (who’s been sited as proof that it causes a problem) doesn’t seem to have a problem with it either.

Trumps… yours is the one that there is a picture of in the other thread, right?

I’m debating what I’m doing right now… I’m converting to 4th gen rear brakes with a 9” install probably over the winter, but right now I need to redo some of the lines and want to install a line lock and a adjustable prop valve at the same time, but I’m debating what problems this will cause with the stock rear drums till i put the disks on (there is a time delay built into the stock combination valve that prevents the front brakes getting any pressure till the rears have a few lbs pressure first).

neagan

iTrader: (7)

.....I'm still hoping someone will address the 1999 Master Cylinder switch.

I think the easiest thing sounds like just having a reputable brake shope do the actual Wilwood proportioning valve.

I replaced all my brake parts on my 88 original 4-disc IROC brakes. I used every part that Ed Miller suggested and am so discouraged with the spungy feel, the faliure of the rear brakes to have enough pressure to even bed the new pads or to get the parking brake to actually hold the car.

Can someone talk about the M/C? Please?????
Thanks, Nitro

MurcoRS

The '99 master cylinder is a direct bolt-on, but you will need to fab brake lines to go from the master cylinder to the prop-valve.
As someone who ran a brake shop for several years I'll warn you that they may be less than interested in doing such a job. Liability lawsuit are all that will pop into the head of a shop manager when he hears this...
It sounds like you have an air bubble in the line running to your back brakes and you can usually get it out using pressure bleeding by a reputable brake shop. The fact that you cannot get the parking brakes to engage either (which doesn't operate by fluid at all, it's strictly mechanical) points directly to the rear calipers themselves as the source of your problems. 82-88 moraine iron calipers never worked well, even when new. Others will heap praise on them but I worked on several of them, and I for one consider them junk. The internal adjusting-ratcheting mechanism for the parking brakes made for a very difficult to maintain system and even regular fluid changes wouldn't flush out the sediment that would accumulate in them, eventually jamming them.

Pat Hall

iTrader: (31)

Putting a 4th gen m/c on is really irrelevant since it's not much different from the 3rd gen style. When you say 88 brakes, are you saying that you have the cast iron calipers on the rear? If so, your best bet would be to upgrade to the 89-up PBR aluminum calipers, along with the correct m/c for 89-up. The 88-down design is hopelessly flawed. They never seem to work right no matter what you do. If you did the 89-up conversion and also had the Wilwood adjustable pv installed, you'd have all around awesome brakes. I'm running the 1LE brakes up front and the PBR aluminum calipers out back on my 89, and I've been extremely happy with the setup. I'm still debating whether to install the Wilwood valve, or the factory 1LE valve. I have both valves, just haven't decided which one to use yet. Since the 1LE valve is a direct bolt-on, I'll probably go with that first. If it doesn't deliver, then I'll go through the hassle of plumbing the Wilwood at that point. When I first put the 1LE's up front, I wasn't very happy with them, but I was using the factory pads. I replaced them with a set of Bosch ceramic pads, and the difference was staggering. Pads can make quite a difference too.

neagan

iTrader: (7)

Pat, does the newer rear caliper have the same hookup for the emergency brake? I figure that the reason the Ebrake dosn't hold much is due to the factory cast iron units not building enough pressure to seat the new hawk pads.
I definitely was having initial issues with getting all the air out of the back lines. I've been told to jack the rear up about two feet off the ground before I try bleeding them once again. Someone else told me to bleed them by 'gravity', which allegedly is slow but sure.
Nitro

Pat Hall

iTrader: (31)

Don't quote me on this, but I'm fairly sure the e-brake cables are different. This is due to the fact that the 88-older calipers are mounted with one in front of the axle, and one behind the axle. The 89-up calipers are mounted behind the axle on both sides. Due to this, the lengths are probably different. I agree with MurcoRS that the problem with the older calipers is mechanical (self-adjusters), and not hydraulically related. If you do upgrade to the newer brakes, you'll need the 89-up m/c for sure. The 88-older disc brake m/c is in a class all it's own. The iron calipers require a lot more fluid volume than the pbr's. Of course the drum m/c for all years will work ok with the pbr's. The 88 disc pv is unique as well. With the pbr rear calipers you can either use the correct pv or the drum brake pv. Either of them supply enough fluid volume to the rears. In fact, I'm still using the drum pv on mine at the moment with no major issues. I've been intentionally putting off installing the 1LE pv since I hate bleeding the lines.

trumps2000

iTrader: (2)

83 Crossfire, Yea I did the splicing with the adj. valve



The stock prop metering provides the delay right. Keeping it should keep the delay. I figured the way I did it, it could always go back together. Might not want to mess with it til you put the rear in though.

83 Crossfire TA

iTrader: (2)

did you mess with the guts of the stock valve?