Tech Request: Brake System Component Selection

Not a Tech Week submission, more like a request that hopefully could help a lot of people.

Looking through all the various vendors and the more I look the confuseder I become.

1> Some recommend a combination valve, some condemn them. Some recommend a metering valve on the front. Some recommend just an adjustable proportioning valve. What do you guys recommend?

2> Is there any advantages using either a Ford style or GM style master cylinder?

3> What are some good donor vehicles for a master cylinder in the 7/8, 15/16 and 1” sizes for a manual disc/drum install? Any parts houses within a hours drive all start with the questions, “What make and year, auto or standard, power windows, baby seat” etc so looking through a book there is not a option, they need a make, model and year.

4> Is a rear residual valve recommended if there is one in the master cylinder or should one in the cylinder be removed? Is there any down side if they are stacked, ie the one in the cylinder and one in line?

5> Are there any manufacturers of residual valves and proportioning valves etc that are recommended and/or avoided? I remember reading that SSB make a good residual valve. How about the rest of the parts?

I know that some of these answers depend on the vehicle, so some of the details on what I am working on. Building a cutting edge Hot Rod 30 coupe using all the latest technology and parts available to a home builder in 1965-6, so disk brakes are part of the picture. Using 57 Ford rear axle and GM Metric callipers in the front. The pedal assembly is a modified F1 unit with a 6 to 1 ratio.

Thanks for the help and thanks from anybody else that can use this info.

Canuck

 

Don't know everything, can only tell you what works in mine. 46 ford p/u. 76 vette non power m/c mounted under the floor, residual valves front & rear & an adjustable valve to the rear brakes. 7/8 bore rear wheel cyl, stock MII calipers up front. truck stops very well, no dive, just squats & stops.
the wheel cylinders for the 9 inch are readily available in a couple of bore /sizes, use the smaller ones (7/8) for best results.
People argue this point...i used 3/16 line to the rear, 1/4 to the front. some say it doesnt matter about line size, some do. Once bled(which is a bitch, m/c is lowest point in the system) pedal is high & hard. Dot 4 fluid, (higher boiling point)
Once again, i can tell you, this setup works for me, you will hear other opinions, i'm sure.

 

Alot has to do with your system. Do you have a disc/drum set-up? All Drum? All Disc?

 

I wonder why some say you need the residual valves. Many early cars had the master under the floor without any special gagets like this and did fine.

 

becuse many early master cylinders had the residual valve built in..many later ones do not

i know that a `40 ford mc had it , and a `65 ford single "fruit jar" does too

i don't beleive the ever popular `67 mustang drum/drum dual does

if the mc does have the residual valve in it , adding another one in line will not hurt anything.

 

36-3window - I think you NAILED IT on the head!!! I'v had fellas SWEAR to me that residual valves aren't needed and they KNOW this because they NEVER ran one - until we keep talking and then find out they had them in their Master- cylinders but never knew it!!!!! First problem - not everyone is familiar enough with their own stuff to know EVERYTHING that is in there!!

The other problem I've noticed is that at times fellas don't understand what parts they are even looking at even do. And then the fact that the factory has used MULTIPLE combination of parts just adds to the confusion.

Canuck,
To answer your questions....

1. Find a similar FACTORY getup and use EVERYTHING they had - it's awfully damn hard to come up with better brake combinations than the factory engineers did.

2. Ford vs. Chevy - nothing particularily different - you really need to look CLOSER at the MC to determine what you want/need. Disc/disc - drum/drum - disc/drum THAT'S what's gonna make the difference not so much so as who's MC it origionally was.

3. Again - it's dependent on your application - On my '47 I used GM calipers with a '77 vette MC - On my Rambler I used a drum/drum master ('67 Camaro)- but took it apart to make sure there were no RPV's internally - then used it on a disc/disc setup - wroks great. The BORE size is not just a thing you pick - it really needs to be considered to work with your pedal ratio and brake system type. Keep this in mind - a drum brake system works in the 500 psi range as a result of the servo effect. Where as a disc setup will operate in teh 1,000 psi range - this doesn't happen by accident - you need to plan for it.

4. I am TOLD (no personal experince) that having "stacked" RPV's can result in "funky" things occurring. I don't know what "funky" is - most Brake experts will reccomend against it - but I'm not exactly sure why.

5. Again - stick with "factory" stuff - they have years of history to reasssure you their designs are well thought out and will stand the test of time.
For instance - we can have :

Metering vlaves - also called "hold off" valves - momentarily delays the pressure to the fronts when using a disc/drum setup.

Proportioning valves - allows a difference of output pressure to provide a maximized braking bias under hard braking - increases your brake effectivity.

Residual Pressure valves - minimizes pedal travel - prevents drums brakes from "sucking" air - used when M/c is mounted LOWER than calipers. AlSO critical when using the LOW DRAG calipers!!!!

Combination valves - a combination of several of the above into one assy.

they all do different things for different reasons in different systems.

 

So would they be required when using 4 wheel drums with a dual master under the floor?

 

Using factory parts is easy on a drum to disk conversion I will be doing on my 64 Malibu, but the hot rod is another story.

So, a MC that matches they rest of the system would be 70’s GM ie a Camaro or Nova Manual Disk Brake, no more than 1”, preferably a bit less. Smaller 7/8 rear wheel cylinders. Residual valves 2 lb front and 10 lb back, insuring there is none in the MC. Lines either 3/16 or 1/4.

The use of a Combination Valve from a similar factory vehicle may be a little hard, I don’t think Ford ever made a A with disk brakes and a Nailhead. How do you match up a similar vehicle or is there another alternative? I noticed in So-Cal's catalogue they state that they have never found one that works correct in a rod.

The sourcing of the residual valves etc is still a problem if I try to stick with the “factory stuff”, what vehicles used them, as a alternative who is the best after market supplier?

Canuck

 

RPV's are almost always a good idea with drum brakes although there will always be people who swear they serve no purpose and in SOME cases they may be right. Back in the old days before RPV's were common place the factory also employed a different approach to prevent the wheel cylinders from "sucking air" and this was a thin shim washer type thing called ( I think) a "lip spreader" - you may have noticed these when taking some older cylinders apart. The factory also stuck RPV's in more places than the M/C - I have seen at least one installed in a "T" fitting they can be kinda sneaky - huh?

Canuck - I missed your origional comment about building a "cutting edge 30 coupe" - and I appreciate your difficulty in emulating a factory getup given these parameters, but the factory DID make some lighter cars - it's all about proper sizing. And as much as we like to make fun of the "roundy round" guys they are pretty serious when it comes to brakes - finding pressure gages for brakes is easy if you look where they buy stuff - this will REALLY alow you to dial your system in. The biggest problem (as I understand it) with building a "rod" and proportioning valves is the LARGE mismatch in tire size. You haven't mentioned this so I don't know if that's part of your equation yet. If it isn't starting with a similar weight car is STILL a good starting point (IMHO) - the factory did make small cars with V8's and short wheel bases - gremlin - cobra2 - I would start studying those just as a reference point.

Lastly given all this I am also gonna suggest you might consider DITCHING the dual reservoir master and INSTEAD go get yourself a '61 chevy truck DUAL BORE master/clutch cylinder and use it with a BALANCE BAR - you can run your RPV's right off the output side and also have ADJUSTABLE balance if you so decide.This would give you an excellent system that would DEFINITELY be period correct. I run one of these on my '34 Plymouth coupe (disc/drum) - they work great!!!

Lately I have heard of guys havign all sorts of problems with Wilwoods RPV's - I've used them (long time ago) never gave me a minutes trouble. Recently I have been buying RPV's from MBM - they seem high quality - only been usign those a short time - so I don't know how well they'll hold up.

 

Best bet: get the whole factory setup.
Next best: Match the front brakes and master, then use wheel cylinder sizing to match the rear. Use the factory pedals if at all possible.

BRACE THE FIREWALL HEAVILY!!!
From cowl to toeboard.​

Combo valves: the factory use 'em, so should you.

Matching braking: Once you're set, drive the car and panic stop it. Note which wheels lock.
If the fronts lock first, increase the bore of the rear wheel cylinders. Opposite if the rears lock first. The reason to adjust the rear is simply due to more wheel cylinder sizes available, in most cases.
If neither wheel locks readily, decrease the bore of the master, or increase the leverage of the pedal.
Once you've got the brakes to stop properly, you MAY add an adjustable proportioning valve to get them perfect. An adjustable valve is NOT to adjust for a badly mismatched setup, it's to fine tune a near-perfect setup.

My own personal best braking car used ALL of the above advice. Ignoring/modifying even one item may result in less than great brakes, IMO.

Cosmo

 

Hemi and Cosmo, some good ideas and lots of food for thought. Like the idea of the small car, Must II or Monza etc. and adjusting the rear cylinder size. Then fine tuning with a adjust prop valve.

Don't have any room for a dual cylinder set up, with the nailhead and SP400 tranny in a skinny A style frame, I am glad I even have room for a brake pedal.

Don't quite understand why I should be bracing the firewall though, I am using a F1 pedal and mount under the floor. Close as I can get to a stock set up as I don't think the A pedals would work.

Canuck

 

Here is recommended for under the floor M/C from Master Power Brakes for disc front and drum rear. The front to rear weight as well as the overall vehicle weight comes into play on part selection as well. The system is adjustable.