For 1971, Ford completed its fourth Mustang redesign, creating a bigger car. It had the basic Mustang look, with a longer wheelbase, stretched length, more width, wider front and rear track and heavier curb weight. A raked windshield, bulging front fenders and aerodynamic enhancements were evident.
The Mach I package returned. It included color-keyed mirrors, a honeycomb grille, color-keyed bumpers, sport lamps, a new gas cap, special decals and tape stripes and black or Argent silver finish on the lower body perimeter. A special hood with NASA style air scoops was a no-cost option with the base 302 cid V-8 and standard otherwise.
Available for the last time was a 429 cid big-block engine, which came in Cobra Jet Ram Air and Super Cobra Jet Ram Air versions. Ford put together 1,255 of the CJ-R equipped Mach Is and 610 of the SCJ-Rs.
Basically a de-stroked Thunderbird / Lincoln 460 V-8, the 429 had a wedge head shaped combustion chamber with up-to-date performance technology. The CJ-R version utilized large valves, a hydraulic camshaft, four-bolt main bearing caps, reworked porting and a 700 cfm Quadraiet carburetor (sourced from General Motors). A Ram Air induction system was included. Advertised horsepower for the 429 CJ-R was 370 at 5400 rpm.
The interior featured large, prominently placed speedometer and tachometer dials while oil pressure, engine temperature, and ammeter gauges were located in the center pod. Below them, stacked, were ventilation and heat controls, the radio, and a clock. Hurst's shifter and linkage easily accommodated the 429-ci engine's power and torque.
The 429 SCJ-R put out 375 hp at 5600 rpm. A Drag Pack option with either a 3.91:1 Traction-Lok differential or a 4.11:1 Detroit Locker axle was mandatory. It also included an oil cooler for when things really got hot at the dragstrip. Other 429 SCJ-R performance features included solid valve lifters, adjustable rocker arms, drop-forged pistons and a 780 cfm Holley carb.
This is the 429-ci C-code engine, the non-ram-air induction model that produced 370 horsepower, compared to 375 with ram air. This huge, heavy engine was responsible for the growth of the 1971 car, increasing front track from 58.5 to 61.5 inches because the 429 Cobra-Jet engine with its canted valves was much wider than the 428-ci CJ it replaced. With this engine and the J-code 429 ram air, weight balance became nearly 60 percent on the front wheels and 40 on the rear.
Both Cobra Jet engines had 11.3:1 compression and produced 450 lb.-ft. of torque at 3400 rpm. The SCJ-R had a bit more camshaft duration (200/300 versus 282/296).