In 1971, the Mach 1 started with a base engine of the 302ci based Windsor motor, with a 2 barrel carburetor, followed by four optional 351 Cleveland engines - the 2-V, 4-V (Venturi), the C.J. (Cobra Jet) and H.O. (High Output) BOSS 351. The H.O. was canceled after mid-year 1971, and shortly thereafter the low-compression 351 'Cobra Jet' became available. At the top were two 429ci options, the CJ (Cobra Jet) & SCJ (Super Cobra Jet). Mach 1s, as well as all other Mustang models (except the BOSS 351) were available with the optional CJ and SCJ motors. The SCJ came with a drag pack V or W code rear gears, oil cooler and a different rotating assembly. 429 Super Cobra Jet engines used 780cfm Holley 4-barrel carburetors, while the Cobra Jet engines utilized GM-sourced Rochester Quadra-Jets.
One of the most recognizable features of the '71-'73 Mustangs is the optional (standard on Boss 351) NACA (NASA) hood design with dual scoops. Though available as a visual, non-functional item, they could be made fully functional on models ordered with the Ram Air option, which included vacuum controlled 'flaps' inside each scoop, and a fiberglass under-hood 'plenum' that directed cool, outside air through a modified, rubber-ringed air filter housing and into the carburetor. The ram-air option included a two-tone hood paint treatment in either 'matte black' or 'argent' (matte silver), coordinated to the base color of the Mach 1 and its decals and striping. In addition, all Ram Air-equipped Mustangs of this generation came equipped with twist-style, chrome-plated hood locking pins.