Combination Adjustable Proportioning Valve and Brake Pressure Switch Part #W260-11179
A proportioning valve is mandatory if you are doing a front drum to disc conversion. An adjustable valve is advisable and if you are installing a rear disc brake kit, it is mandatory. The adjustable valve allows you to dial in proper rear brake pressure. The factory proportioning valve does not recognize your new rear brake conversion. So rather than hoping all this will work properly, install an adjustable valve in line to the rear brakes and remove the factory valve. You can effectively dial in your brakes.
So this is how you should run your brake lines if you are using an adjustable valve.
For the front brakes – run the front line out of the master cylinder (generally the small port) to the proportioning valve. The valve is marked front line in. On the bottom of the valve the ports will read front out. Then install the front brake lines from the valve (marked accordingly) to the front wheels. For the rear brakes run a line from the master cylinder to the proportioning valve marked rear in. Install the line going to the rear end in the proportioning valve marked rear out. If you are still using rear drum brakes you will need a 2 pound residual valve part # W260-3278. Install this after the proportioning valve. The residual valve is used only with drum brakes. If you are using rear discs, you will not need the residual valve.
Note: There is a pressure switch installed in the proportioning valve that will turn on your brake lights when pressure is applied. This is great if you are using this valve on an old hot rod. If you are installing this valve on a car that has a switch on the pedal, you will not need to run power to the switch.