Wilwood Right-Mounted Valve and 1-1/8-Inch Black Tandem Master Cylinder with Mustang Manual Pushrod

The larger compact tandem bore is combined with the Mustang manual input in this black kit. Its right-side valve arrangement requires the matching line routing and sufficient clearance around the master assembly. Established in 1977 by Bill Wood, Wilwood Engineering designs and manufactures disc brake systems from its base in Camarillo, California. Calipers, fittings, rotors, valves, master cylinders and brake lines serve its motorsport, street-performance and specialized applications. The full assembly, including its mating connections and operating requirements, governs the correct part selection.

Technical Details

• Manufacturer part number: 261-15666-BK
• Material: Aluminum
• Cylinder bore: 1-1/8"
• Pressure circuits: 2
• Stroke Length: 1.10 in
• Reservoir Type: Integral tandem chambers, 7.8 and 4.7 oz
• Fluid capacity: 7.8 / 4.7 oz
• Flange-to-end length: 6.55"
• Overall Length: 12.32"
• Mounting centers: 3.22–3.40"
• Pushrod dimensions: 5.75"
• Finish: Black E-coat
• 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, right-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

Confirm the classic Mustang pedal and mounting points. Check the 1-1/8-inch bore against pedal effort, leverage and caliper fluid requirements.

Wilwood’s kit summary gives a 1964–1973 Ford/Mustang range, while the corresponding bare-master family identifies 1964–1972. Confirm the actual manual pedal, supplied eyelet and mounting geometry, particularly for 1973, before ordering.

Manufacturer Documents

• Wilwood product specifications
• Wilwood FL162 instructions and specifications
• Wilwood DS1287 instructions and specifications
• Wilwood DS1178 instructions and specifications
• Wilwood FL311 instructions and specifications

With more than 20 years of experience, PMB Performance can help compare the specified part with the assembly you are servicing. Include the existing part identification and relevant hydraulic dimensions.