It's no secret that hot rodders love horsepower; there's nothing quite like the exhilaration of acceleration. Well, that's not exactly true-making a panic stop can crank up the adrenaline output almost as effectively. The big difference between the two is that standing on the gas and getting pushed back in the seat is normally done for fun, while rapid deceleration is often done in desperation.

Today most street rods have plenty of horsepower to get them going, but they don't always have commensurate stopping power. Ironically, the problem often turns out not to be the brakes themselves, but the hydraulic system that activates them. To improve stopping power it's not unusual for street rods to be equipped with vacuum power boosters, particularly when disc brakes are employed, however sometimes the results don't meet the expectations.

Vacuum boosters use the difference between atmospheric pressure and the engine's manifold vacuum to increase the force delivered to the master cylinder from the pedal. How much of an increase is dependent on two factors: manifold vacuum and the effective size of the diaphragm in the booster. With all things equal (vacuum, pedal ratio, master cylinder bore), an 11-inch booster will raise the pressure in the system as much as three times more than a 7-inch booster. Unfortunately, the tight confines of most street rod engine compartments, or the under floor area that most master cylinders are relegated to, can make it difficult to fit an appropriately sized power unit. However, now there is an alternative to a large-diameter booster for big gains in hydraulic pressure in the form of an electric power brake unit from ABS.

Found on a number of contemporary high-end automobiles, electric power brakes are proven to be effective and reliable. No vacuum or belt-driven pumps are required and the entire ABS system consists of three components-a compact electric power supply, a special master cylinder, and an accumulator, which is the source of the boost for the braking system. Measuring only 8x6x6 inches, the power unit can be hidden anywhere in the vehicle, in any orientation, just so long as it is below the brake fluid reservoir. It has two hydraulic connections, the gravity feed from the reservoir and the high-pressure assist line that gets plumbed back to the port on the master cylinder with the accumulator inline. The integral pressure switch and relay come pre-wired, requiring only a ground, a battery connection, and a keyed ignition connection. According to ABS the pump draws 14 amps at maximum pressure and is quieter than most aftermarket electric fuel pumps. The unique master cylinder has a 1-3/16-inch bore, which means the fluid volume is adequate for the most complex systems with multi-piston calipers, while still being able to create 1,600- to 1,800-psi brake line pressure during normal operation and over 2,000 psi at maximum output. Finally there's a hydraulic accumulator that provides for very smooth actuation of the brakes. It also provides reserve pressure to assist the brakes if for some reason the electrical power to the pump is interrupted. The accumulator will supply pressure for as many as 20 brake applications, after that the brakes function as though they were non-boosted. In operation, fluid is delivered from the master cylinder reservoir to an electric pump where it is pressurized and delivered to an accumulator. When the driver steps on the brake pedal and the pushrod moves forward, a valve inside the master cylinder opens and pressurized fluid from the accumulator enters a chamber in the master cylinder behind the piston assembly and helps apply the brakes. A switch monitors the pressure in the accumulator, and turns on the electric pump when pressure drops below a preset minimum and shuts it off when pressure is back up to a preset maximum.