Technical Brake question

Just starting to lay out brake lines on my '36 Chevy coupe project and I have a simple question. Would it be a benefit to me to install front and rear residual pressure valves even tho my master is mounted on the firewall? I am using a 1" bore, non-power dual reservoir master with a hanging underdash pedal, disc/drum setup with 3/16" lines and I was thinking that maybe the valves would help keep the slack out of the pedal...'specially with standard brakes.
I'm eager to hear any opinion, and I appreciate your time and experiance.
KenO

 

Depending on wheel cylinder design, you may need them on the rear, they are of no value to you on the front. If the wheel cylinders are built with cup expanders then no need in the rear either. If you are unsure then install them on the rear anyways.


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I was digging thru my brake fittings when I found the valves and adjustable proporting valve, which got me thinking about using them in the first place. Its not gonna cost me anything to install them, so maybe I will...can't hurt, right???

 

I haven't found a need for them....maybe I'm not picky enough.

 

No benefit but just another few joints to leak

 

.....starting to sound like I'm over-thinking it. Thank you, gentlemen.

 

The addition of an adjustable prop valve in a custom disc/drum system allows for some front/rear brake balance to help ensure the rears do not lock before the fronts, because of the pressure operating differences of discs and drums. There really is no good reason not to install one.

 

First you need to find out if there is a residual valve already in the master cylinder. You should be able to see it in the threaded port that the line for the rear brakes screws into.

 

For sure figure out if the master already has one.I have read of guys putting a 2 lb. residual in the front line to cure a soft brake pedal.It would be trial,and error to find out.

 

A disc brake 2 lb. residual is not necessary when the master cylinder is high mounted above the calipers.

 

The brake experts like ECI say if there is a valve already in the master, and you add another, its OK.

Most of the wheel cylinders I see nowadays don't have the springs or expander inside them. So the RPV couldn't hurt.

 

So it sounds like I should put the adjustable proportioning valve in for the rear, thats fine. I've included a picture of the cylinder I bought and would also appreciate confirmation that the forwardmost reservoir is for the front brakes.
Would I be able to push a gas welding tip cleaner into the port and feel resistance to check for a valve????

 

Interesting, almost every one I see that is relatively modern has cup expanders, either wound on the end of the spring or a separate piece, residual valves virtually vanished in oem applications long before drum brakes fell out of common use.


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I have yet to use one on a car with the master on the firewall, like someone else said, more joints to leak.
Just saw the Corvette "style" master. I have come to the conclusion that they are questionable and almost any brakes-gone-bad post will have them being used. I use standard GM or Ford masters in my builds.

 

Welding tip cleaner or a straightened out paper clip can be used to check if there's a residual valve in the master cylinder. Just slide it into the port where the line screws on. If there's no valve it will go in all the way. If there is a valve you'll feel an obstruction just past the seat that the brake line seals against.
Line placement on the master cylinder- If one of the reservoirs is bigger that would be the one for the front brakes because disks brakes use a larger volume of fluid. If you happen to have a drum/drum master cylinder that has a residual valve on both ports you'll need to remove it from the front brake port or your disk brakes will drag.