Adjustable Proportioning Value Block
Nothing beats a braking system with an adjustable proportioning block. They are vastly preferable to the factory-style metering valves, which are prone to sticking and over-centering with age. The valve assembly is available in a chrome finish. However, I chose the black one because the car will have a blackout appearance.
Most kits include the following components: Valve, with Mounting Hardware, Mounting Bracket Pigtail electrical wiring for brake light switch Pre-Bent 3/8-24 thread 3/16″ Brake Lines from Master Cylinder to Valves 5- 3/16″ Inverted Flare Tube Nuts.
Installing the valve. Mount the Valve with the Knob Facing Away
When mounting the valve, the switch should face front while the adjustment knob should face backward. This will ensure that the adjustment knob is easily accessible on the left and that the port labeled rear output faces the firewall.
This port is placed in front of the brake light switch. On a Corvette-style master cylinder, the port for the front brakes will be the port furthest from the mounting tabs. This port is placed between the brake light switch and the adjustment knob. The valve also includes a port labeled rear input. On a master cylinder designed for a Corvette, the port for the rear brakes will be situated closest to the mounting tabs.
You will need to mockup the pre-bent lines to ensure that they are linked to the correct ports, as their shapes change significantly. Utilize a flare nut wrench when tightening brake lines to prevent rounding off the nuts or kinking the lines. The clearance for the lines where they enter the valve can be rather restricted, therefore you may want a thinner flare nut wrench. Many high-end wrenches are thinner in this location, making it easier to tighten the lines.
The only remaining step is to choose the sort of lines or hoses to connect the valve to the rest of your brakes. The valve also has two ports labeled front outlet. Two ports are supplied if you need to run separate front brake lines or if you’re using a TEE to split the front lines. When running a single line to the front brakes, you can plug any unused port with a 3/8-24 inverted flare male plug.
Notes on Bleeding and Adjusting the Brakes
Using an adjustable proportioning valve to bleed the brakes is a simple process, but there are a few procedures to take to ensure everything goes properly. After bleeding the master cylinder on the bench, ensure that the valve is fully open to enable full pressure to the back brakes.
When adjusting your braking system, begin with the Valve fully open so that the back brakes are at maximum pressure. Start with some heavy braking at about 30 mph in a safe area to determine how well the brakes are functioning. Unfortunately, there is no magic setting, as every vehicle is different due to brake components, vehicle weight, balance, and wheel and tire sizes. 60-70 percent of the braking force should be on the front wheels, so move the Valve clockwise to increase rear brake pressure and counterclockwise to decrease rear brake pressure. When the Valve is properly adjusted, the front and rear brakes should be identical, with neither locking up before the other. Once you’ve adjusted it, you won’t need to make any other adjustments unless you change wheel and tire combinations or need to tweak the braking for track day competition driving.