Holds a 10 pound pre-load on your brake caliper pistons, which isn't enough to apply your brakes, but makes them apply quicker when demanded.
A residual pressure valve can be 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). Balance bar systems require the appropriate valve just outside the master cylinder.