The Biscaynes factory manual-drum system is glaringly devoid of technology. The single-chamber master cylinder pushes fluid through a single line into a distribution block (arrow). The block has three outlets; two supply pressure to each of the front wheel cylinders, and the third (toward the rear of the car) pressurizes the rear brakes. Yep, if this style of master cylinder goes south, youre left with no hydraulic brake system. Thats a good enough reason to swap it out for the GM-style SSB dual-reservoir master, which has separate circuits for the front and rear brakes.