hello, ive decided to freshen up my current brake master and remove the power booster from my 59 Apache....currently mid 80's monte setup. im convinced in running a 67-76 'Vette manual brake master cylinder, but i cant find a listing or any info on wether or not i need a proportioning valve. my front set up is a late 70's Camaro clip(77 or so) and rear disc brake late 80's Iroc axle. my local autozone has the master but no listing for a proportioning valve. what should i be looking for...thank you.
Just because Autozone doesn't sell them, doesn't mean you shouldn't use one. I got by with an adjustable one, but it was far from perfect. This time around, I am using a factory combination valve. Go take it off of that IROC.
thanks for the info. now i know i do need one. the rear end has been on there for years now and im looking to walk in and get one off the shelf...i did not want to order one from ecklers but you gotta do what you gotta do. finding an Iroc with rear discs may be a task too. thanks again.
OK, here's where I throw a monkey wrench in the works...I've built (and driven last summer, 2009, over 7,000 miles) a '55 Cadillac with a '78 Trans Am disc brake front end...using a Corvette master (disc/drum combo) and a 7 inch power booster...the rear is a stock '55 Cadillac with drum brakes...I don't have a proportioning valve...I didn't install one...and have not had a problem with the brakes or stopping. To see the build, go here: http://www.jalopyjournal.com/forum/showthread.php?t=329070&highlight=the+best+55+caddy+build R-
ive four wheel disc brakes and ran a monte master/booster combo meant for disc/drum for years...go figure.
If it works go with it, what I am figuring is your either front or rear brakes may wear out faster because pressure is being applied at the same time in the same amount to both front and back, a 55 Caddy is a big car so you may not feel the car tipping forward because its equally begin stopped, but as long as you know that a combination valve is missing if you ever start having break problems, that will be the 1st thing to check.
Just to be a bit clearer on the subject, there is a bit of a difference between proportional valve and combination valve, even though they look similar. I prefer a combination valve, and if you comparison shop a combination valve will cost the same as a proportional valve but offers more. There are 2 things I always make sure I don't skimp on the brakes and steering. Link with pictures. http://www.cl***icperform.com/TechBook/BrakeTroubleshoot.htm The Right Valves Using the correct valving for your application is critical to the proper operation of your brake system. There are four types of valves that perform different functions to the brake system. . Metering Valves These valves are used to equalize braking action of a Disc/Drum brake system by preventing the disc brakes from applying until about 75 - 135 psi has built up in the lines. This delays the disc brakes and allows the drums to catch up. This provides rear stability on wet surfaces and reduces front pad wear. Metering valves are generally located in the lines to the disc brakes. In most of our kits, the metering valve is a part of the combination/prop valve. Proportioning Valves The function of the proportioning valve is to limit pressure to the rear brakes relative to pedal force, especially when high pressure is required to apply the front disc. This prevents the rear wheels from locking up as weight is shifted forward during braking. Proportioning Valves are generally located in the brake line to the rear brakes and sometimes are incorporated into the master cylinder. They are available as either preset or adjustable valves. Note that adjustable proportioning valves are not DOT approved for street driving and should only be used for racing applications! Residual Check Valves These valves are used to hold a certain amount of pressure in the lines even when the pedal is not pressed. This is a sort of preload line pressure to activate the brakes more quickly. They will give a higher, harder and more responsive pedal. Residual check valves should not be used as a subs***ute for a properly functioning system. For instance, do not use residual check valves in place of complete and proper bleeding procedures as presented in this guide and our Brake Bleeding Guide. Check valves will most likely be necessary when the master cylinder is lower than the calipers or hard lines run higher than the master cylinder fluid level. In disc brakes a 2 lb. residual check valve prevents fluid from flowing back without causing the brakes to drag. With drum brakes, a 10 lb. valve is used to compensate for return spring tension in the drums. Residual Pressure Valves are generally color coded blue for 2 lb. and red for 10 lb. for easy identification. Combination Valves These valves offer multiple functionality in a single unit. They combine the functions of both a metering valve and a proportioning valve with the addition of a brake light warning switch. The brake light warning switch signals when there is an imbalance of pressure in the system caused by a problem in the front or rear brakes. By far the best valve to use for all disc brake conversions. All our kits use DOT approved Combination Valves designed specifically for either Disc/Disc or Disc/Drum applications.
I use the pv4 and pv2 combo valves with the corvette style master. MBM sells a low buck valve and mount kit for 75$
to answer 32Rules and 2nd the question of his about disc/drum combo for this purported vette m/c - there are NO Corvettes with disc/drum setup - 64 was last year for drums all around (could be ordered on 65s until factory stock was depleted) and 65 was first year for discs on all four corners. There is a reason proportioning valves are used - and they work exactly the way they're meant to. Just because you haven't experienced a downside...doesn't mean you shouldn't have one in your system. dj
After seeing what propwash posted, I guess I misunderstood, or misheard what was told to me then...perhaps it was a Camaro dual set-up...at any rate, the brakes work very well...I put a lot of miles on my car during the summers, so I'll keep an eye on the brakes to see which end wears out faster... R-
hello, is it a bad idea to run an aftermarket adjustable proportioning valve to the rear using the vette master? any ideas good or bad? since my set up is closer to Camaro im looking at an iroc combo valve or an adjustable one from ssb.
The reason midyear corvettes didn't use proportioning valves is because the system was engineered and sized to be that way. To put it simple, the front and rear caliper bores are sized such that combined with the bore size of the master cylinder, the effective front to rear pressure is ideal for the corvette's particular CG height, weight distribution, etc...so the proportioning is already built in.... Not trying to sound like a dousch- I just like this sort of stuff....
in this thread swade mentions a master that doe s70/30 http://www.jalopyjournal.com/forum/showthread.php?t=523047&highlight=adjustable+proportioning+valve
on my 53 ford car,im using a vette master,the front is a s10,the rear calipers are ford explorer.when i installed the set up i didnt add a valve of any kind just to have a starting point. it has a great pedal and stops straight, ive had it in rain and have had to make some emergency stops....i wont change a thing. now i'll add another rig,,84 jeep cj7,used 1 ton gm front calipers,same explorer rear calipers and used the stock jeep (disc-drum) master. but left the stock prop valve. also had great pedal,stopped straight ...
I would suggest that possibly the reason they didn't use them then wasn't so much that they "perfectly" balanced their system, but rather simply hadn't advanced to that level of braking yet. The PV adjusts the pressure balance ACROSS the range - there is no single perfect balance point - for any one car. Weight transfer changes the tire load - tire load changes the amount of braking a tire can do - the proportioning valve tries to optimize this changing relationship at various braking loads. Meaning that while you may have a 60/40 relationship at a moderate pedal and a 70/30 at a heavy breaking pedal pressure. Why does it matter? Well if conditions are always the same - it doesn't matter as much, but when they change then it does come into play even more. Panic stopping on wet pavement is an entirely different equation than panic stopping on dry pavement. That's one reason why road cars have adjustable brake balance at the driver's control. Rain, snow, gravel, dirt roads - all are quite different in terms of what you would want for optimal braking. Most get it close and call it "good" - and it probably is, but I wouldn't put it up against Detroit's finest either.
well i have a few options: -manual vette master with aftermarket prop. valve -manual vette master with 87 iroc disc/disc p.v. -master/booster/p.v. from 87 iroc -if i have to manual vette master with 74-77 vette pv. **curently my pedal gets ****ed down to the floor when i turn on my truck so thats what brought all this about. any recomendations?
I don't use them on any of the systems I have built, and I have had NO PROBLEMS ever, on pavement, dirt, gravel, wet conditions etc. I used to install adjustable prop valves, but I found that they did little to nothing to change the braking, and after a few of them leaked, I chose to leave them off of all the cars I have built since then.
this is the kind of info i could not find. i ran that master/booster combo for years and it stopped hard but never spun out. i understand its an art but should i stay with the current set up and add a Iroc prop valve? ill check the adjustment on the pedal rod but i keep reading that ****ing the pedal all the way down is a booster problem. thanks again for all the ideas.
I have front/rear discs and put in adj prop valve. I have it fullly open and it stops well enough from 40mph to about kill me if I slam on the brakes. My plan is to test it from highway speed someplace safe. If the rear doesn't come around or lock up first I'll be decently happy. That said I remember a car craft challenge or something where one of the entrants lost the braking part because they couldn't get their 4wdb prop valve figured out. Cant remember if it was adjustable or not.
As stated before about running without proportioning vavle I also do not use one on my 56'. I use to have one, but like it better this way. As always no two differant cars get set up the same. My comb is 68-72 A body front disc, stock 56 11" rear drums and 1" manual vette master.
The Jalopy Journal
