When engine-bay space is tight, measure from the mounting flange. Wilwood 261-15523-BK uses the compact Mustang-pushrod tandem master cylinder, only 6.55 inches from flange to end, with a black valve and left-side bracket. That shorter body still needs room for the tubes, valve, lid and a correctly moving pedal.
What is in the box
- Black E-coat aluminum tandem master cylinder with a 15/16-inch bore, 1.10-inch stroke and integral 7.8 / 4.7-ounce reservoirs.
- Mustang pushrod with clevis/eyelet end, combination proportioning valve, left-hand mounting bracket, stainless connection tubes with preinstalled tube nuts and the specified mounting hardware.
- The master-cylinder instructions list one 9/16-18, one 1/2-20 and two 3/8-24 inverted-flare line adapters, two unused-port plugs and crush washers. Vehicle lines, fluid and required residual-pressure valves are separate.
Match it to the build
Match the mounting slots, Mustang pedal eyelet, pushrod geometry, bore and engine-bay clearance on the actual manual-brake build. Wilwood’s exact kit page states 1964-73, while its Classic Mustang family page states 1964-72. Compatibility for 1973 remains unconfirmed; obtain exact vehicle and brake-configuration confirmation before ordering. DS-1288 explicitly lists this kit and restricts it to custom performance/racing/special-purpose off-road brake systems, not an OEM direct replacement.
Before installation
- Verify the slotted mount, pedal eyelet and pushrod geometry. DS-1288 requires the full 1.10-inch stroke before the pedal reaches the floor, carpet or another stop, and full piston return with the rod remaining captured when released.
- Use the drawing to check the 6.55-inch flange-to-end envelope; the valve and left-hand bracket add their own clearance needs.
- Choose the correct 1/2-20 outlet ports and supplied inverted-flare adapters for double-flared lines only. Follow the specified crush-washer sealing procedure; do not add thread sealant or substitute single flares.
- Plumb the primary circuit to the end with the greater effective caliper piston area as instructed, and set front/rear bias for the actual system. Drum circuits need a separate 10-pound residual valve; a low-mounted disc reservoir may need the specified 2- or 4-pound valve.
- Bench bleed the cylinder level, then bleed and test the complete system with a qualified brake installer. Wilwood requires factory service for internal rebuild work; it is not a user-serviceable rebuild.
