Few car companies manage to produce vehicle that obtains its own legend – a car so rare, boasting so much power and mythos, that even the average layperson has heard its name in passing. We’re talking about the 1969 Boss 429 Mustang, often referred to as simply the “Boss 9” by blue oval enthusiasts. Arguably one of the rarest and most coveted muscle cars of the era, the Boss 429 features a motor that edged out Dodge’s own Hemi 426. But, to beat the best, Ford wouldn’t steal from the best… Would they?
They would. And they did, although to say Ford ripped off Chrysler isn’t entirely fair. Dodge’s Hemi motors are named so because of their design: The motor gets its power from a rounded, hemispherical combustion chamber and domed cylinder head. Now, the hemi motor design is not Dodge’s bread and butter. The design was originally drawn up in 1901, by one car maker named Pipe. The hemi motor saw its first performance action in the 1907 Grand Prix, and again in Peugeot’s and Alfa Romeo’s track cars in 1912 and 1914. The design was so popular it got picked up by a certain British car maker named Daimler. Yes, the Daimler company that eventually merged with one Chrysler motor company – A.K.A MOPAR. So there you have it. Ford renamed their own hemispherical motor’s design element the “Crescent”.
Or, not quite. We’re not implying the mythical Boss 429 is a Hemi thief, an unoriginal power house. It is certainly the coolest Mustang made in the 60’s (yes, we think so, even compared to the GT500), and it boasts some of Ford’s Best engineering. It truly is a one-off creation worth its weight in gold. The Boss 9 incorporated aluminum heads, a first for any muscle car at the time, as well as a monstrous four-barrel carb rated at 735 CFM, mounted on an aluminum intake manifold. This is the same top end air and valve management stuff that we are now seeing on modern S197 and S550 Mustangs.
While the car was conservatively rated at an anemic 375 horsepower, the actual figure the motor put out was reported to be well over 500 ponies. That’s coming out of a naturally aspirated motor. Again, these are numbers we’re seeing on current Shelby cars – cars with the latest engineering, high-tech ECUs, dynamic timing management, and big blowers. This alone yields the legend of the Boss 9. But making this monster motor fit in a Mustang body required some innovation. Ford’s designers enlisted the same folks who built the Cobra Jets and Mach 1s of the day. They had to modify those existing chassis to accept the giant 429 block and 4-speed manual transmission. Modifications included widened shocks and strut tower braces, a relocated battery, inner fender extensions, and change to the existing motor mounts.
A uniquely geared, 3.91 ratio version of Ford’s rear Trac-Lok differential helped plant all that power to the rear wheels. But for all this powertrain development, the Boss 9’s exterior retained relatively production-like, mute options. The car was only offered in five colors: Raven Black, Wimbledon White, Royal Maroon, Candy Apple Red, and Black Jade. The only designation giving away what was under the hood was a small, exterior decal that red “Boss 429”. Most Mustang enthusiasts agree that the Boss 429 was simultaneously one of Ford’s greatest power horses, and one of the most “sleeper”-inspired rides the big blue oval produced. Just 859 were built and registered, with current Boss 9s fetching nearly $500,000 at auction. Break out that second mortgage – if you can even find one for sale.
