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).
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).