General Information
The Boss 429 Mustang is a high performance Ford Mustang variant that was offered by Ford in 1969 and 1970.
The Boss 429 (also known as the "Boss 9" by enthusiasts[citation needed]) is arguably one of the rarest and most valued muscle cars to date.[1] In total there were 1358 original Boss 429s made. The origin of the Boss 429 came 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. It used four-bolt mains, a forged steel crank and forged steel connecting rods. The engine featured aluminum cylinder heads, with a modified Hemi type combustion chamber which Ford called "crescent". These heads used the "dry-deck" method, meaning no head gaskets were used. Each cylinder, oil passage and water passage had an individual "O" ring style seal to seal it tight. The Boss 429 engine used a single Holley 4-barrel carburetor rated at 735 CFM mounted on an aluminum intake manifold that flowed well for its time.[2] 1969 cars featured a hydraulic lifter camshaft while 1970 models got a mechanical lifter camshaft along with an improved dual exhaust system though rated power output stayed the same.
The Mustang's engine compartment was not wide enough to accommodate the massive Boss 429 engine. As a result Ford assigned Kar Kraft of Dearborn, MI to modify 4 speed Cobra Jet Mustangs to accept the new Boss 429 Engine. Kar Kraft was a Ford exclusive contracted experimental vehicle facility that functioned as Vehicle Engineering for Ford Special Vehicles. Kar Kraft had previously developed the first GT40 MKII's (winner of the 1966 24 Hours of Le Mans) and designed and built the GT40 MKIV's (winner of the 1967 24 Hours of Le Mans).
Production of the Boss 429 began in 1968 at Kar Kraft's new assembly plant in Brighton, Michigan; the cars were transported to this plant directly from the Ford Rouge plant. The new, revised, front apron assemblies that accepted the large Boss 429 engine had been installed by the Rouge plant as the base vehicles were being built; this produced a stronger and cleaner front structure. The reworked front fenders were also installed at the Rouge plant.
Next the battery was repositioned to the trunk and a stiff 3/4" sway bar was added to rear end to improve handling since the car was now nose heavy. This was the first Mustang ever fitted with a rear sway bar, and it notably handled much better than other big-block Mustangs of the time, making it a very capable track car. It came fitted with an 8,000rpm tachometer, and AM only radio. In addition, a hole was cut in the hood, and a manually controlled hood scoop was added to these cars. Other features included a front spoiler that was shallower than the Boss 302 spoiler, color keyed dual racing mirrors, and an engine oil cooler. It was also equipped with a 3.91 ratio rear axle with a "Traction-Lock" limited slip differential.
The Boss 429 (also known as the "Boss 9" by enthusiasts[citation needed]) is arguably one of the rarest and most valued muscle cars to date.[1] In total there were 1358 original Boss 429s made. The origin of the Boss 429 came 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. It used four-bolt mains, a forged steel crank and forged steel connecting rods. The engine featured aluminum cylinder heads, with a modified Hemi type combustion chamber which Ford called "crescent". These heads used the "dry-deck" method, meaning no head gaskets were used. Each cylinder, oil passage and water passage had an individual "O" ring style seal to seal it tight. The Boss 429 engine used a single Holley 4-barrel carburetor rated at 735 CFM mounted on an aluminum intake manifold that flowed well for its time.[2] 1969 cars featured a hydraulic lifter camshaft while 1970 models got a mechanical lifter camshaft along with an improved dual exhaust system though rated power output stayed the same.
The Mustang's engine compartment was not wide enough to accommodate the massive Boss 429 engine. As a result Ford assigned Kar Kraft of Dearborn, MI to modify 4 speed Cobra Jet Mustangs to accept the new Boss 429 Engine. Kar Kraft was a Ford exclusive contracted experimental vehicle facility that functioned as Vehicle Engineering for Ford Special Vehicles. Kar Kraft had previously developed the first GT40 MKII's (winner of the 1966 24 Hours of Le Mans) and designed and built the GT40 MKIV's (winner of the 1967 24 Hours of Le Mans).
Production of the Boss 429 began in 1968 at Kar Kraft's new assembly plant in Brighton, Michigan; the cars were transported to this plant directly from the Ford Rouge plant. The new, revised, front apron assemblies that accepted the large Boss 429 engine had been installed by the Rouge plant as the base vehicles were being built; this produced a stronger and cleaner front structure. The reworked front fenders were also installed at the Rouge plant.
Next the battery was repositioned to the trunk and a stiff 3/4" sway bar was added to rear end to improve handling since the car was now nose heavy. This was the first Mustang ever fitted with a rear sway bar, and it notably handled much better than other big-block Mustangs of the time, making it a very capable track car. It came fitted with an 8,000rpm tachometer, and AM only radio. In addition, a hole was cut in the hood, and a manually controlled hood scoop was added to these cars. Other features included a front spoiler that was shallower than the Boss 302 spoiler, color keyed dual racing mirrors, and an engine oil cooler. It was also equipped with a 3.91 ratio rear axle with a "Traction-Lock" limited slip differential.
