Small GM stock proportioning valve / junction block - Does it have residual valving?

Basically what the ***le says.

I've heard that if I were to use the stock type proportioning valve from a similarly weighted car or small pickup that they should be able to maintain the correct pressures at the front rotors and at the rear drums.

Anyone heard something similar, or is there any truth to this?

I know 30 years ago my dad used a '59 Chevy pickup under the floor of my '29 RPU and it has Pinto discs up front and drums in the rear, and uses the stock Pinto junction block/proportioning valve and has never had any problems with the brakes energizing properly.

Just wanting to know before I spend the money to buy the residual valves. I'd rather use what I've got on hand if I can. Know what I mean?

 

A stock combination valve for a car with the same type of brakes (such as disk front/drum rear) should have the necessary residual pressure valves in it.

 

It is my understanding that true residual valves are only necessary for master cylinders that are below the wheel cylinders.

Modern combination valves contain a metering valve (applies pressure to rear drums first), proportioning valve (reduces pressure to rear drums), and pressure differential switch (brake problem indicator light)

Rich

 

So, what you guys are saying is that if I used the stock proportioning valve - say out of an S10 pickup - in my floor mounted master cylinder setup, with front discs and drum 9" rear - that I should be okay without specialty residual valves?

Just making sure I understand completely.

 

I believe that you would still need residual valves if the master cylinder is below the wheel cylinders.

Modern combo valves don't need residual valves because the the master cylinder (firewall mounted) is always above the wheel cylinders.

Rich

 

He's saying they don't use them in newer cars....since the master is mounted higher than the brakes. A little bit of research show's he's right.

So you probably need them....

 

****... oh well.

So, just one valve inline for each end, or one valve per corner? In other words - 2 or 4 of them needed?

 

You probably need 3, if that's how many lines connect from the proportioning valve to the brakes. Two fronts, one rear.

 

Frome the Wilwood site...

A residual pressure valve is used when a master cylinder is mounted equal to or below
the horizontal plane of the calipers or drum brake wheel cylinders. This valve prevents
fluid flow-back to the master cylinder reservoir which can cause excessive brake travel
or “pumping” of the pedal to engage brakes.

Install the valve as close as possible to the master cylinder and position the end marked
“M.C.” toward the master cylinder and the end marked “OUT” toward the brakes. Ports
in the valve are 1/8-27 NPT threads and will accept standard inverted flare tube
nut adapters.

A 2 lb. valve is designed for disc brakes and a 10 lb. valve for drum brakes. If the vehicle
has a single outlet master cylinder and a disc/disc system, only one 2 lb. valve is
required. If the vehicle has a single outlet master cylinder and a disc/drum system, a 2
lb. valve is required in the disc brake line and a 10 lb. valve in the drum brake line (after​

the tee fitting).

 

I'd strongly recommend ordering eci residuals they are far superior to willwoods and speedways imho.

 

will just need 2 valves a 2lb and 10lb

 

The residual check value is internally in the master cylinder or a valve screw in the port on the master cylinder. Its used for drum brakes to keep some pressure in the rear wheel cylinders. It is also used to keep fluid in the line when the master is below the wheel cylinders or calipers, you may already have a residual valve in your master cylinder for the rear brakes.

 

This web site below has a good cross section of a GM proportioning valve. It shows the metering valve for the front brakes but no reisidual valves.

http://www.carolinacl***ictrucks.com/81-87-GM-FS-Truck-Prop-Valve.html