On This Day In History
Saturday 21st November 1970
The rarest of Ford Mustangs, the Boss 351, debuted at the Detroit Auto Show in Michigan. The car, with eye-catching looks aided by a 60-degree sloping fastback, was powered by a fierce 5.4 litre, 330-bhp, 8-cylinder engine built on Ford’s new ‘Cleveland’ block. The Boss 351 was manufactured for just a single production year, 1971, and only 1,806 units were made, compared with the 500,000 Mustangs manufactured and sold by Ford in 1965 alone.
The Boss 351’s main claim to fame was its R-code V-8, whose 330hp at 5,400 rpm and 370-lbs.ft. of torque at 4,000 rpm would outgun a number of big-blocks. But the engine was just the beginning of the Boss’s goodness. The 351 was bolted up to a Hurst-shifted four-speed manual transmission, with a Traction-Lok 9-inch rear end equipped with 3.91:1 gears. All came with the beefed-up Competition Suspension package and power front disc brakes. Externally, they were marked by their twin, functional “NASA” hood ducts, Mach 1 honeycomb grille, lower body paint treatment, bodyside stripes and 351 decals.
The original Boss Mustangs, the 302 and 429, were introduced in 1969, developed for Ford by Kar Kraft Engineering of Brighton, Michigan. The Boss 302 duked it out with Chevrolet’s hot Z/28 Camaro in Trans-Am racing, while its big brother made it possible for Ford to legalize the big-block engine for NASCAR racing. By 1970, the handwriting was on the wall for the muscle-car era, as rising insurance premiums and ever-tighter safety and emissions requirements took effect. Mustang sales, which had once exceeded 600,000, had slumped to 190,727 in 1970. No one could have been too surprised when both Boss Mustang were cancelled in 1970, in connection with Ford’s withdrawal from factory-supported racing, but the blow was softened with the introduction of the Boss 351 in the fall of that year. It would be a last hurrah for out-and-out small-block performance, a last call for the true muscle car believers.
The Mustang body introduced in 1971 was larger and heavier than the previous year’s, as Ford traded the athletic grace of its Falcon-based predecessor for an engine bay large enough to comfortably swallow the biggest of the company’s big-block V-8s–something that had been a challenge with the earlier cars. Ford recognized, too, that its pony car buyers were maturing and starting families, and would appreciate the extra room that the larger body offered. The body style, which lasted through 1973 until the introduction of the Mustang II, was larger in every dimension, and turned off some of the earlier car’s fans. “The 1971-1973 cars do not get the respect they deserve,” argues Don Prochot, the owner of our feature car, and we have to agree. That the car has not yet become a favorite among collectors has a silver lining for its fans, though, because prices of all but the most sought-after models remain affordable.
The Boss 351 was the premier performance Mustang for 1971, stickering at $4,124, or a premium of more than $1,000 above a base Mustang Sports Roof. That big pile of money bought performance: Motor Trend recorded a quarter-mile time of 13.8 seconds, while Car and Driver reported that the car “offers dragstrip performance that most cars with 100 cubic inches more displacement will envy.” In fact, Sports Car Graphic found that a 1971 Mach 1 equipped with a 429 Cobra Jet engine just nipped the Boss 351 in a race from zero to 60mph, 6.3 seconds to 6.6, despite its 78-cubic-inch advantage. Add in the fact that most critics considered the small-block car to be better balanced, and it becomes clear that the Boss was the car to beat.
The critics loved the new Boss. “The ’71 Mustang is a long way from the refined Falcon-based Mustang we all gaped at in 1964, and for that, present Mustang owners can be happy,” said Hot Rod in its February, 1971 issue. “This one feels like it it’s taking on the size of a Torino (and in some ways, it is), but no matter what its shape or size may resemble, it sure looks like a racer. The Boss 351 is going to salt away a few Z/28s before its season is up.” “In the atmosphere of ordinary driving, the Boss 351 was a real joy,” agreed Super Stock and Drag Illustrated in its March, 1971 issue. “Its looks and absolutely unique idle were attention-getters like those of few other cars in recent memory.”
At first glance, the Boss 351 bears a resemblance to its stablemate, the Mach 1, but with “Boss 351 Mustang” decals on the front fenders and tail and a larger blacked-out area on the hood. The main way to determine whether the car you’re looking at is a genuine, bona-fide Mustang is to look at the VIN: the fifth character should be an “R,” designating the high-output Boss 351 engine.