Wilwood Combination Proportioning Valve substantially simplifies mounting, plumbing, wiring and brake proportioning adjustments on vehicles with custom brake systems. The combination block maintains full isolation between front and rear fluid circuits and can be used in conjunction with an tandem outlet or dual mount master cylinder assemblies. The rear circuit has a single inlet and single outlet with the adjustable proportioning valve. The front circuit has a single inlet with two outlets. It can be run as a single outlet with one outlet plugged, or used to split the plumbing on its way to the calipers. The brake light switch is immediately activated by pressure in the front circuit. The sturdy forged body incorporates two 5/16" through holes for secure mounting to the frame or a reinforced chassis brace.