1. This is why you should change your master cylinder to dual chamber type. If you blow a brake line with the single-chamber master cylinder, all braking is lost. With the dual-chamber type, only half the system is lost, and you can still stop the car. The dual-chamber casting measures about seven inches from mounting flange to end of casting, while the fruit jar is about five and a half inches from mounting flange to the end of the casting. The dual-chamber, 7/8-inch bore master will increase line pressure, and stop the car with less effort than the one-inch bore, single-chamber fruit jar.
2. The under-floor brake pedal operates the fruit jar mounted on
a bracket between the frame and transmission. Notice the brake light switch threads into the bottom of the casting boss. It
will need to be relocated by T'ing it into either the front or rear brake line.
3. You can tell from the bumps in the lid which chamber is larger. The chamber nearest the mounting face is for front disc brakes (larger chamber), and can also be used for front drum brakes by installing a residual check valve for that chamber.
4. Late-model cars are now equipped with diagonally split master cylinders, which means each reservoir has two ports. The bottom ports (to the rear drums) have large, residual check valves, while the top ports go to the front discs. The diagonally-split system is used on front-wheel-drive cars, where 85 percent of braking is done with the front wheels. For greater braking capability (as opposed to a front-to-rear split), one front and one rear wheel will always be stopping the car.
5. Adapters shown on the end of the two brake lines (and in the outlet ports) will be needed, since the ports are larger than the 3/8-24 brake line fining. The right port is H2-20 thread, while the left port is R16-24.
6. Before 1968, the residual check valve was in the cylinder
bore, and disassembly was required for its removal when used for disc brake applications (arrow). Afterwards, the check valves (the two assemblies at bottom of photo) were placed in the outlet ports behind the visible, inverted flare seats for the brake lines, and can now be removed with a small screw, shown in one of the inverted flares.