Photo: YouTube/John Clay Wolfe
In the late ’60s, Ford was on a high-performance engine rampage, releasing ever more powerful (and larger) engines to counter the nefarious Chrysler 426 Hemi terror. After the 428 Cobra Jet and its “Super” brother, which came out in 1967, the next step up the ladder was the legendary 429, introduced for the 1968 model year. The larger Cobra Jets were great engines, but that still wasn’t enough. In 1969, Ford went all out and dropped the biggest hammer they ever built during the Golden Era: the Boss 429.
The reason for building the world-shattering big-block 429 was to make it ready for NASCAR, where the Hemi was winning victories and championships with virtually no competition. In 1969, the Charger Daytona rose to fame. FoMoCo bosses had learned the important lesson they had taught Chrysler in 1965, when the race Hemi was banned after Ford complained that the engine with the hemispherical cylinder heads had no road correspondent.
Mother Mopar introduced the Hemi for the street in 1966 and outdid everyone else. Ford couldn’t fall into its own trap and the big 429 was produced in sufficient numbers to win the approval of NASCAR officials. Thus was born the Boss 429 engine, one of the Blue Oval’s most coveted powerplants.
A very limited production run of 857 units satisfied homologation requirements (the governing body for stock racing required that at least 500 cars be sold to regular civilians). They are much rarer than a Hemi car and just as sought after, as the Boss Nine was only on the market for two years (1969 and 1970).
Photo: YouTube/John Clay Wolfe
The Big Boss also had a little brother, the Little Boss, the 302. It was built for the same purpose as the Big Block: to homologate it – but for SCCA (in other words Trans Am) racing. However, despite the same availability time, it reached much higher production numbers. While the Boss 429 only reached 1,368 units in the two years it was produced, the Boss 302 reached 8,641 units.
Ford recognized the nameplate’s potential and didn’t simply retire the Boss name after 1970, even though both the 429 and 302 disappeared from the scene forever. In 1971, the third – and least known – member of the Boss triad was released – the Boss 351. In keeping with the tradition of incorporating displacement into the name, the final Boss was based on a 351 Cleveland V8 introduced in late 1969 for the 1970 model year.
In its specific Boss application, the 351 developed 330 horsepower thanks to its 11.7:1 compression ratio—a configuration exclusive to the 1971 Boss, although the engine was used in all other Mustang models in the lineup, including the Mach 1. This last model was the longest-running type in this Boss-Mach series, lasting from 1969 to 1978 (with two more iterations between 2003-2004 and 2021-2023).
Photo: YouTube/John Clay Wolfe
Finding one of the three would be a jackpot for any collector, but finding all three under one barn roof is nothing short of the holy grail. Well, miracles do happen from time to time, and John Clay Wolfe of Give me the chassis number will attest to this with his latest barn find. A 1969 Boss 429, a 1971 Boss 351 and a 1971 Mach 1 — which had been lying hidden somewhere in Glen Rose, Texas, for at least two decades — have surfaced with great potential for restoration.
The condition of the cars is encouraging to say the least – the red Mach 1 starts immediately and even its power windows work. The yellow Boss 351 needs some work (its carburetor and valve train are covered in rags, but otherwise the Mustang looks solid and clean). The royal brown Boss 429 is by far the crown jewel, and features some rare original equipment not often found on other examples on the market.
The air cleaner snorkel and exhaust system (pump and canister) were removed from the super-powerful 429 cubic-inch V8 to allow it to reach its full potential. The seven-liter powerhouse was officially rated at a paltry 375 hp and 450 lb-ft (380 PS, 610 Nm), but its true potential was far higher. This particular example has the original odometer reading of 28,527 miles (45,910 km) and the previous owner had it since the early ’80s.
Photo: YouTube/John Clay Wolfe
Second in terms of sales is the Boss 351. With 1,806 units produced, this was the rarest series of the Mustang line in 1971 and was equipped with a mandatory four-speed wide-ratio transmission and a 3.91 Traction-Lok rear differential.
For special use on the racetrack or track, the 351 Cleveland could be equipped with oil cooling hardware and special valves (made of titanium – the intakes – or of special steel alloys – the exhausts). Interestingly, the 1971 Boss Mustang was the only model that had no direct connection to racing, as it was built specifically as a street model (albeit a high-performance one).
And finally, the 1971 Mach 1 is another gem that ranks among Ford’s all-time legendary products: the 429 Cobra Jet decals on the side of the dual hood scoop need no introduction. Seven liters of high-performance engine in a Mach 1 were not a common sight that year.
Photo: YouTube/John Clay Wolfe
Of the 151,000 Mustangs built, 36,500 bore the Mach 1 badge, but only 815 of those were ordered with the big-block V8. To put it in perspective, its rarity surpasses that of both the Boss 351 of the same year and the Boss 429 of 1969.
Like all barn finds, these cars require repairs to bring them back to top shape. However, these are not just any old Ford Mustangs from that era; they are special models that usually change hands between people who have both the means and the will to take care of them.
