It's a scenario that happens all too often. For weeks, or perhaps months, you plan a transformation for your favorite Mopar by significantly increasing its horsepower. Maybe you are installing a shopping cart full of high performance goodies on your existing mill or swapping it for a more potent powerplant. Perhaps you're going to extremes and stuffing a wild 440 into an engine bay once occupied by a Slant Six. Regardless of the recipe you've concocted, you spend days performing the work and still more time tuning and extracting performance from your new combination. As time passes, your tweaking pays off. Your car is now running better than it ever has. Then it happens, you're blasting down the road and the Generic Motors piece in the next lane has disappeared from your side mirror and is now visible only in your rearview. Your Mopar is pulling strong and sounding great. But just when it seems all is right with the world, a truck enters the roadway in front of you. Instantly your foot snaps from the carburetor's secondaries and pummels the brake pedal. What a time to find out your antiquated drum brake system is no longer up to the task of safely stopping your ride.
Before you begin, your car...
Before you begin, your car must be supported by the frame on jackstands. After removing the cotter pin and castle nut from the outer tie-rod end, a few sharp blows to the steering arm should jar the tapered stud from its hole in the arm.
If this has ever happened to you (and you survived), you've probably considered some brake system upgrades. Factory-style disc brakes might seem the most logical choice. but what cars would be suitable donors, and how involved would such an operation be? Follow along, and we'll guide you through. Though we'll cover the steps necessary to convert A-, B-, and E-Bodies to disc brakes, we'll concentrate on the A-Body for this transplant, as it is a bit more involved than a B- or E-Body swap.
A-Body
There are two different disc brake configurations found on A-Bodies. The earlier style-offered as optional equipment through 1972-was the four-piston Kelsey-Hayes setup. The second style-used from 1973-1976-was the single piston slider-type caliper used with 10 7/8-inch rotors. Both styles used 14-inch wheels. If you're after an original appearance, then use the four-piston style. It uses the same control arms and upper ball joints as the drum brake setup, and will allow you to retain the 4-inch lug circle of your drum brake car. Keep in mind the lower ball joint is different. This setup will look original on a pre-'73 A-Body, however, parts tend to be expensive and hard to find.
Disconnect the brake hose...
Disconnect the brake hose from the steel line at the framerail (a clip retains the hose to the tab on the framerail), then remove the brake drum.
Place a jack under the lower...
Place a jack under the lower control arm near the lower ball joint and jack upward until the upper control arm rises from its bumper. This will relieve the tension on the ball joints.
The steering knuckle is attached...
The steering knuckle is attached to the lower ball joint by two bolts, which also pass through the backing plate. Remove them.
The upper ball joint can be...
The upper ball joint can be separated from the knuckle in the same manner as the tie-rod end. A ball joint separator or pickle fork makes the job easier, though the ball-joint boot will usually be destroyed. (We opted for the ball-joint separator since we replaced the ball joints while the front end was apart.) With the upper ball joint disconnected, the knuckle and brake assembly can be discarded.
A-Bodies use different lower...
A-Bodies use different lower ball joints between disc- and drum-brake applications, so ours had to be changed. B- and E-Bodies use the same ball joints in all applications. Again, we opted for the ball-joint separator, though a few sharp blows to the lower control arm with a heavy hammer would have done the job.
Install and torque the replacement...
Install and torque the replacement lower-ball-joint nut and cotter pin.
The disc-brake steering knuckle...
The disc-brake steering knuckle can now be installed. Be sure to torque all fasteners and install new cotter pins in the upper ball joint and outer tie-rod end.
Install the disc-brake dust...
Install the disc-brake dust shield next.
Early style four-piston calipers...
Early style four-piston calipers use a steel line to join the rubber hose to the caliper. A bracket is used to support the hose and eliminate stress on the steel line. The bracket attaches to the caliper mounting bolts.