Brake Residual Valves
 

Adding a dual master cylinder with adapter to my 40 Ford with stock drum brakes. Need to add 10lb. residual valve in the line. My question is I am keeping the stock 1/4" brake lines but can't seem to find valves made for that size line only for 3/16 lines. Does anyone make them or will I have to use some type of adapter fitting. Thanks for your help.

Re: Brake Residual Valves
 

If it helps Sacramento vintage ford sell adapters for 3/16 to 1/4, part no. 12005-15 or 1/4 to 3/16, part no. 12005-16

Re: Brake Residual Valves
 

Speedway has them. 1/8'NPT both ends for use with a suitable fitting for whatever size tubing being used.

http://www.speedwaymotors.com/Speedw...hed,32110.html

Re: Brake Residual Valves
 

Thanks Weemark and 51 Merc-Ct for taking the time to respond I will check out both dealers.

Re: Brake Residual Valves
 

I'm a little confused as to where you have been looking, most of the residual valves I have used can be fitted with about any connector you would be interested in. Wilwood is an example. Try any of the suppliers such as Jegs, Summit, Speedway, etc.

Re: Brake Residual Valves
 

Confused? Apparently you did not read post #3 :confused:

Re: Brake Residual Valves
 

I was referring to post #1 where the OP stated "...can't seem to find valves made for that size line only for 3/16 lines. Does anyone make them or will I have to use some type of adapter fitting."

You need to read the whole thread! I just found it a little odd that RAF was having difficulty finding the type of fitting he was wanting as they as so common and just about every supplier I know of carries them. Thought maybe there was something more to the issue, but apparently not.

Re: Brake Residual Valves
 

RAF some dual master cylinders have built in residual valves. I use early Mustang drum-drum that have them.
John

Re: Brake Residual Valves
 

Good point!

Re: Brake Residual Valves
 

I use 2 different dual MC's for drum/drum on my customer chassis. One exits on the left and one on the right and both of them have residual valves built in. One is Chevrolet and one is Jeep and they have equal sized reservoirs front and rear.

Re: Brake Residual Valves
 

I bought 2 valves at Summit Will wood the valves that came with my dual
master cylinder were imported junk no matter how tight I made the fittings
they still leaked

Re: Brake Residual Valves
 

some of the american cars that are disc/drum don't have residual valves in the drum section of the mcyl, but the wheel cylinders have expanders on the springs that keep the cups pressed to the walls of the cylinder

Re: Brake Residual Valves
 

You can use the early dual chamber Mustang MC which has residual valves built into it. I did that when I had a Mustang rear and F-100 fronts. Why not use the stock master cylinder if you are using drums all the way around?

Re: Brake Residual Valves
 

I wonder why we think a residue pressure valve is needed ? I don't think the stock `40 Ford hydraulics used them.
you will need to reduce from the 1/4" Ford brake line to go into the 3/16" fittings on the modern dual master anyway.

Re: Brake Residual Valves
 

You will need the proper fitting, but this is not a reducer issue, the master cylinder fittings are much larger than 3/16 or 1/4 (and often different sizes between the front and rear fittings). Adapter is probably a better term.

Re: Brake Residual Valves
 

The main purpose of drum brake residuals is to prevent air from entering past the wheel cylinder cups during fast release. They were used on all drum brakes up to the mid '70s, including '40 Fords.

Re: Brake Residual Valves
 

First time I've ever heard that. I've been doing brake
service work and brake design work for more than
40 years. (Global West, Akebono Brake Corporation, etc)
Residual valves are used in brake circuits to keep
drum shoes in close proximity to drums. They are
also used when master cylinders are mounted in a
vehicle application where they are physically lower
than calipers to keep fluid from draining back into
the master.

Re: Brake Residual Valves
 

They also hold fluid in the line, which helps to maintain a high , firm pedal, and this helps also to reduce the response time.
With regard the fast release letting air in: It is the return springs on the shoes that force the pistons back. The pistons push the cups back. The cups push the fluid back, and the fluid keeps the cup lips sealing against the bore.
The Residual line pressure valve in the master cylinder maintains this low pressure (probably about 2 psi???) Years ago the wheel cylinder cups also had metal expanders to assist in this task.
Earlier in this thread was a picture of an aftermarket line pressure valve that holds 10 psi. This seems like a lot to me. Can someone explain to me what its proper purpose is?

Re: Brake Residual Valves
 

10 psi are used with drum brakes and 2 psi are used with disc brakes. From Wilwood:

"Inline residual pressure valves from Wilwood retain a minimum brake line pressure to help eliminate excessive pedal travel.

... 2 lb. valves are used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers.

With drum brakes, 10 lb. valves are used to compensate for return spring tension in the drums."

Re: Brake Residual Valves
 

1948F-1Pickup,
Do you really believe a 10-15 lb (approx. normal OE production range) residual valve can overcome shoe return springs of 50-100 lbs or more? :confused: The "keeps the shoes in close proximity to drums" makes no sense at all, (although is/was shared by some misinformed brake suppliers) as the normal shoe to drum total clearance is .025"-.030". That's .0125"-.015" per shoe. The shoes in a drum brake should always return solid to their anchors, by design.
My 35 year dynamic brake testing experience started in '71 at Bendix, when residual valves began a phase out because of cup expanders, better cup designs, and front disc brakes that do not need residuals.

Bluebell,
I do agree with your first sentence, and is why I install/recommend residuals on all drum brake systems. :-)
It is the very strong shoe return springs that can and will allow air to enter past the cylinder cups during fast release, fact-not opinion.
Production residual valves ranged from around 10 lbs to about 18 lbs from the info I've been able to gather. The after market in line valves are all rated 10 lbs for drums, and 2 lb for discs.
Production disc brakes never needed or used residuals, as master cylinder location was high on the firewall before modern discs were available. The aftermarket 2 lb valve should only be used when the calipers are higher than the master.
Early single system residual (check) valves were usually located at the end of the bore, but most dual masters have the valves located behind the tube seat(s).