Guide To A-Body Disc Brake Swaps

Global West’s Pro Vintage kit uses late fullsize car steering knuckles, negative-roll upper control arms with Del-A-Lum bushings, big Wilwood Superlite II four-piston cast or billet (shown) calipers with 1.75-inch od pistons, and 1.25-inch-thick x 11.75-, 12-, or 13-inch-od (shown) ventilated rotors on alloy hubs.

Master Power sells factory-style disc-brake upgrades with all-new parts. Complete kits include a master cylinder, a combination valve, a power booster, steering knuckles, caliper mounting brackets, calipers, pads, rotors, bearings, seals, hoses, and an instruction video. Nonpower kits are available too.

Stainless Steel Brakes gets a drop on the competition with its 2-inch-dropped knuckle kits. The kits include knuckles with cast-in caliper mounting brackets, calipers, rotors, pads, bearings, seals, flex lines, a power booster, a master cylinder, an adjustable proportioning valve, and all necessary hardware.

The most practical salvage yard- based A-body disc brake conversion uses later-model 11- or 12-inch rotors and corresponding knuckles with Moraine iron single-piston calipers.

In most cases, the special tie-rod ends and different-taper upper and lower ball joints in H-O Enterprises’ kit are the only aftermarket components required for an econo A-body disc-brake conversion.

H-O Enterprises’ kit SB-55 uses 1979 Grand Prix tie-rod ends (shown) to attach the late knuckle to1964-1970 A-bodies; use kit SB-56 with 1973 A-body tie-rod ends for 1971-1972 A-bodies.

Not only is the late knuckle (right) much beefier than the old GM A-car drum-brake knuckle (left), its 1-1/4-inch-taller height alters the upper A-arm angle, thereby raising the roll center and allowing desirable negative camber curves with today’s wide radials.

Figure on adding about 3/4-inch worth of alignment shims when installing the new knuckle and retaining the stock upper control arm. Moog offset control arm shafts can help too.

Due to their different taper, the late knuckles require corresponding late ball joints. The bolt-in uppers are no problem. However, the fit of the late press-fit bottom ball joint is a tad too tight in the old A-body lower arm, so retrofit kit makers turn the new joint down to the correct dimensions in a lathe.

Baer front brake kits bolt to stock drum- or disc-brake knuckles. They can be ordered preassembled on modified 1978-1996 B-car knuckles suitable for use with a Hotchkis upper arm conversion. This photo shows the front Track setup with the optional Touring rear disc brakes.

Run out of alignment shim space, or just want a full negative-roll camber curve? Global West’s kit includes custom tubular upper A-arms with revised geometry, ball joints, tie-rod ends, Del-A-Lum bushings, and even an angle arm support bracket to help vise-press the pivot bushings into the reused stock lower arms.

There are two holes on most old GM A-body brake pedals--the top hole offers more pedal advantage (leverage) and should be used with nonpower brakes. Use the bottom hole with power brakes.

H-O Enterprises prefers the 1970-1974 Camaro/Firebird manual master cylinder (Hollander Salvage Yard Interchange No. 417) for nonpower A-body disc-brake retrofits. Nonpower disc-brake master-cylinder conversion kits complete with new pedal pushrod are also available from Master Power.

Retrofit late-model 11- and 12-inch knuckles sometimes have bumpsteer problems. Due to altered geometry, the tie rod can’t travel in the same arc as the knuckle’s steering arm. Baer sells Tracker bumpsteer adjustable tie-rod sets to minimize this problem.

If running different-size front and rear tire combos or for competition applications, adjustable proportioning valves are available from Wilwood and other disc-brake conversion specialists.

Wilwood’s heavy-duty front disc-brake kit uses Dynalite II racing four-piston calipers on 10.75-inch rotors with aluminum hubs. The calipers are available with cast-aluminum housings or with billet housings; the latter come jet-black (shown) for max heat rejection, or polished for that show-car look.