While the Boss 302 was intended to be a perfectly balanced road race car, the Ford Mustang Boss 429 had a decidedly different mission in life – uncompromised acceleration. Although the exterior appearance was similar to that of the Boss 302, the 429 engine under the hood was a heavily detuned version of a new Ford NASCAR racing powerplant.
The choice of Mustang as the model used to meet the 429’s homologation requirements – rules dictating a certain number of a manufacturer’s stock car engines were actually sold in production vehicles – was considered unusual given that Torino was Ford’s NASCAR flagship at the time. Plus, the effort required to shoehorn the huge 429 between the narrow Mustang shock towers dictated that the cars were heavily modified under the skin – work farmed out to Ford vendor Kar Kraft. Much of the front suspension was re-engineered to make the transplant work, and the battery was relocated to the trunk to provide additional room.
Even with special chassis bracing and a unique rear sway bar, the “Boss Nine” was at its best when pointed in a straight line: With a few owner modifications to undo the factory detuning, the car could yield quarter-mile times in the low-12-second range. That performance, coupled with big-block appeal and low production numbers, has conspired to make the Boss 429 perhaps the peak of Mustang collectability.
1969-70 Ford Mustang Boss 429 specifications:
- 429-cubic-inch (7.0-liter) OHV V8
- 375 hp / 5200rpm
- 450 lb.-ft. / 3400rpm
- Four-speed manual