Muscle Car Brake Upgrades. Bobby Kimbrough

There is nothing good about a single-line master cylinder. If there is a leak in one of the four wheel cylinders or damage to a line occurs, the vehicle’s overall braking capabilities will be lessened. Stepping up to a dual-port master cylinder that separates the front and rear brake circuits is a much safer system and should be high on the list of future upgrades.

      A dual master cylinder, often referred to as tandem, splits the front and the rear system, which keeps the two systems separate to maintain braking function if one system fails. These have two outlets, one for the rear with the other for the front.

      For street applications, go with a tandem design that has separate outlets for the front brakes and the rear. When selecting a master cylinder, determine whether you plan to run power assist or stick with manual brakes. There are a few typical bore sizes, such as 7/8-, 15/16-, or 1-inch diameters and the varying bore size will have an effect on the pedal feel.

       In a tandem master cylinder, brake fluid is secured in two independent reservoirs. If one brake circuit fails, the other will continue functioning properly. Notice the ports that direct fluid into the cylinder chamber.

       A popular place to mount the master cylinder on street rods is to the chassis right under the driver-side floor pan. This bracket assembly is being fit on an early 1950s Chevy.

      A larger bore will create more displacement or volume but requires more pedal force, while a smaller bore will produce more pressure. There is no one guideline when selecting a master cylinder because there are so many variables on each vehicle, such as the calipers, weight, suspension, and even seat position. Use components from a single source since manufacturers design and engineer their products to work together.

       Selecting a Master Cylinder

       Selecting the proper master cylinder for your application is key to the overall performance of the system and feel of the brake pedal. Review your goals with the brake manufacturer before making a choice.

      Selecting a master cylinder is not only important for the operation of the brake system but it also affects the pedal feel. This is where knowing the pedal ratio and the force used comes into play. You may like a firm pedal feel, but what if you’re building a street rod and your better half drives it, will they welcome the stiff pedal as well?

      Keep in mind that a larger cylinder bore creates more fluid volume, while a smaller cylinder produces more pressure. If you’re going to have a very short pedal ratio, a smaller cylinder may create a brake system with little feel or modulation. In fact, it will become more of an on/off feel with little in between. Conversely, a softer, longer pedal may be slow reacting and take too much movement to effectively slow the vehicle.

      This is where it is important to discuss your plans and goals with the manufacturers, especially when it comes to the master cylinder. ■

Power Assist

      In the brake system world, there are either manual brakes or power-assisted brakes. Manual brakes have a harder, definitely firm, pedal feel because you’re dealing strictly with the mechanical contact and hydraulic force within the master cylinder and the geometry of the pedal and rod assembly.

      Many original high-power muscle cars were ordered with manual brakes for simplicity and less weight (or had cams that were too big to make enough engine vacuum to support a booster). Older street rods also may choose the manual route simply due to the packaging under the hood. However, most rods these days (and even many muscle cars) are going with some form of power assist on their brake systems. Remember, disc brake systems require more pressure than drums (approximately 900 to 1,200 psi) to function as designed, so in the majority of cases, assist is a nice feature.