Wilwood Left-Valve Master Cylinder Kit for Classic Ford Mustang Manual Brakes, Bare 7/8-inch Bore

This bare High Volume Tandem kit includes the eyelet-style pushrod for the early Ford Mustang manual-brake arrangement. The 7/8-inch master is combined with a left-hand proportioning valve, bracket, formed tubes and fasteners. Wilwood Engineering, the Camarillo, California disc brake manufacturer founded by Bill Wood in 1977, designs and builds systems for specialized, motorsport and street-performance applications. The product range covers brake lines, valves, fittings, calipers, master cylinders and rotors. A replacement component must preserve the intended relationship between the system's hydraulic and mechanical parts.

Technical Details

• Manufacturer part number: 261-13272
• Material: Aluminum
• Cylinder bore: 7/8"
• Pressure circuits: 2
• Stroke Length: 1.10 in
• Reservoir Type: Integral
• Fluid capacity: 8.0 / 4.8 oz
• Flange-to-end length: 8.15"
• Overall Length: 13.65"
• Mounting centers: 3.22–3.40"
• Pushrod dimensions: 5.75"
• Finish: Bare
• Native pressure ports: 1/2-20 at both circuits; use the correct included outlet adapters and seal washers
• Circuit outlet adapters: Primary: 3/8-24 or 1/2-20 inverted flare; secondary: 3/8-24 or 9/16-18 inverted flare
• Hydraulic relationship: Equal pressure output from the two circuits before external proportioning; 2:1 primary/secondary volume relationship
• Service: Factory rebuild only; do not disassemble the tandem piston assembly
• Kit contents: Master cylinder, left-side combination proportioning valve and bracket, formed stainless connecting tubes and mounting hardware
• Combination-valve functions: Adjustable rear pressure, isolated front/rear circuits, front-line junction and hydraulic brake-light switch

Fitment & Compatibility

Match the actual Mustang manual pedal and eyelet geometry; the corresponding master family identifies 1964–1972 applications. A modified pedal, booster or converted brake system requires its own geometry and hydraulic checks, including clearance around the left valve.

Manufacturer Documents

• Wilwood product specifications
• Wilwood DS985 instructions and specifications
• Wilwood FL331 instructions and specifications
• Wilwood FL162 instructions and specifications
• Wilwood DS487 instructions and specifications

PMB Performance brings over 20 years of brake-system experience to component selection. Send the installed cylinder, pedal and connection details if you need help checking this configuration.