Alright, if any of you read my last blog on the world’s most powerful production truck, you might gather that I am in a high horsepower mood this Thursday. In accordance with this need for power, it is only fitting that I choose one of the highest horsepower Mustang’s every to roll off the assembly line for the newest installment of Muscle Car of the Week. The 1969 Boss 429.

For those that had to have the biggest and baddest Mustang, the Boss 429 was clearly the best choice. But how did this monster of a muscle car come about? The answer to this question as well as several other questions regarding past muscle cars is this: racing. Ah yes, racing inspired the creation of so many of my favorite muscle cars: the Cuda AAR, Boss 302 and Dodge Daytona to name a few. You see, the Hemi cars of the day were absolutely cleaning up on the oval track and Ford teams were tired of getting worked over by the MOPAR bunch. Ford adopted the ‘if you can’t beat em…’ strategy and developed a motor that used similar (not the same, but similar) engineering as the Hemi. They did this by making semi-hemispherical race heads (the Ford boys called them ‘crescent’ heads) and bolting them onto a Ford block, thus the Boss 429 was born. Because of the unique resemblance of the head ports to a side-by-side double-barrel shotgun, the 429 motor is also referred to as the ‘Shotgun 429′ by some enthusiasts.

As it was with all new race motors, NASCAR required the factory build at least 500 production units for sale to the public before any an engine was allowed to legally race on the track, a process known as homologation. Workers at the Brighton, Michigan Kar-Kraft assembly plant started building each Boss 429 by hand in January of 1969 and finished in July after building 859 units, two of which were actually Boss 429 Mercury Cougars.

The 429 motor itself was a beast on the track however disappointed many on the street. Because this was a race motor from the start, Ford engineers had to detune it by giving it a weak cam, small carb and smog pump in order to keep rising insurance costs down. Factory rated at 375 horsepower and 450 pound feet of torque the Boss 429 suffered in terms of street performance because it couldn’t get up into the high revs where most of its power waited. On the race track however, the 429 could really stretch its legs and get up into the high rpm’s to take advantage of that high end power. As most true street racers know, one needs low end power for good launches as speeds rarely exceed 100 mph in a standard stoplight drag race. This made the 429 vulnerable to its brother the 428 Cobra Jet and other Detroit big blocks of the day.

Even with a mediocre street record Boss 429’s are incredibly rare as only a total of 1359 were made through the two production runs in 1969. Because of this the legend of the beefy Boss 429 Mustang continues to grow and prime low-mile examples continue to climb higher and higher towards 7 figures. Big_Blocker out.