Muscle Cars - Ford Boss 429 Mustang

ford boss 429 mustang grillesThe Boss 429 is arguably one of the rarest and most valued muscle cars to date. In total there were 1,358 Boss 429s made. The origin of the Boss 429 comes about as a result of NASCAR. Ford was seeking to develop a Hemi engine that could compete with the famed 426 Hemi from Chrysler in NASCAR's Sprint Cup Series (then known as "Grand National Division"). NASCAR's homologation rules required that at least 500 cars be fitted with this motor and sold to the general public. After much consideration, it was decided by Ford that the Mustang would be the car that would house this new engine. The Boss 429 engine was derived from the Ford 385 engine.

The Mustang's body however was not wide enough to encompass the massive Boss 429 engine and as a result, Ford hired Kar Kraft out of Dearborn, MI to modify existing 428 Cobra Jet Mach 1 Mustangs to properly fit the new Boss 429 engine. Kar Kraft was contracted by Ford to create the Boss 429, because Ford was stretching itself thin across a number of projects. Kar Kraft at the time was in the process of creating the Trans-Am Boss 302. Production on the Boss 429 began in 1968 in Brighton, Michigan at Kar-Kraft's factory; the cars were transported to this plant directly from the auto maker's plant and the work began.

ford boss 429 mustang tail lightsKar Kraft made extensive modifications to the Mustang, including widening the shock towers and extended out the inner fenders to allow this massive engine to fit. The mounts for the front suspension were chopped and displaced to create room for the block and exhaust manifolds. Next the battery was repositioned to the trunk and a stiff sway bar was added to rear end. In addition, a hole was cut in the hood and a manual controlled hood scoop was added to these cars. These cars were rated conservatively at 375 hp and 450 lb/ft of torque. Actual output was well over 500 horsepower. The manufacturers and dealers only listed 375 hp because of legal issues and rising insurance costs.

Both model years featured a toned down exterior, as compared to other Mustangs of the era, in that the only external identification of the car were the Boss 429 decals on the front fenders, aft of the front tires. The rest of the car featured a very clean look that was atypical of most Mustangs that Ford had produced. To show just how special these cars were, they were given special Nascar identification that was placed on the driver's side door. Each car was given a "KK" number which stood for Kar Kraft. KK #1201 was the first Boss 429 and KK #2558 was the last Boss 429 made. Holding a big block with a huge bore and hemispherical combustion chambers, the motor had staggering potential for power.

ford boss 429 mustang wheelsThe finished product was still strong, rated at 375 horsepower at 5200 RPM, but the powerband was narrow for an engine of this size, a result of the restrictions. Stoplight drag racing was prevalent in the day, and owners of these Mustangs, as well as other cars such as Chrysler's street Hemi, could be surprised by "lesser" cars of the day that produced broader powerbands and more low-rpm torque. 100+ horsepower can easily be added with the right cam, air intake, carb, exhaust selection, along with a broader powerband. While power steering was a "mandatory option" on the Boss 429, neither an automatic transmission nor air conditioning was available.

In the case of the latter, there simply wasn't enough room under the hood. The 429 engine was unlike any other Ford motor, being much wider in the cylinder head, thanks to its semi-Hemi combustion chamber design, and this meant strut towers needed widening and the battery relocating to the trunk. The Boss used the 'Top Loader' close-ratio, four-speed manual because the autos couldn't handle the torque. The suspension had uprated springs and shocks plus an anti-roll bar. Some Boss 429s may have this silver tape stripe missing; a small brass plate was substituted by Kar Kraft on a small number of cars.