ford mustang boss 429 side profile shot
(Image/BOSS429.JPG by CJ DUBCC BY-SA 2.0 CA)

 If you’re a fan of the #3 Mustang on our list of all-time greats, you can thank…Mopar???


Truth is there is plenty of credit to go around for the 1969 Boss 429 Mustang, but the impetus for the legendary “Boss 9”  was Chrysler’s 426 HEMI engine. Ford was looking to develop a hemispherical engine that could compete with the 426 Elephant, which was highly successful in NASCAR’s then Grand National Division. The end result was one of rarest and most-valued muscle cars of all time: the Boss 429 Mustang.

The 1969 Ford Mustang Boss 429 was powered by Ford’s new 429-cubic-inch engine, which featured semi-hemispherical combustion chambers. To meet NASCAR’s homologation rules, which required a minimum production run of 500 cars, Ford made just 859 Boss 429s for 1969. It’s a good thing, too, because it took a lot of doing to shoehorn the “Semi-Hemi” engine into a Mustang.

To get the massive engine—an engine that would’ve been better suited for a Torino—to fit into a smaller Ford Mustang, Ford contracted out to Kar Kraft Engineering of Dearborn, MI. The team at Kar Kraft heavily modified Ford’s existing 428 Cobra Jet and Super Cobra Jet Mach1 Mustangs to accommodate the big block. They widened the shock towers, extended out the inner fenders, chopped and displaced the motor mounts, and relocated the battery to the trunk. They also lowered the suspension, which ultimately made the Boss 429 a better-handling muscle car than many of its counterparts.

In other words, the Boss 429 was essentially hand-built.

The 1969 “Boss 9” was rated conservatively at 375 horsepower and 450 ft.-lbs. of torque, but actual output was thought to be well over 500 horsepower. Each of the rare 859 Boss 429s was given special NASCAR identification, which was placed on the driver’s side door. And in 2013, an unrestored 1969 Mustang Boss 429 sold for $417,000 at a Mecum auto auction.

That’s 417,000 more reasons the 1969 Ford Mustang Boss 429 lands in our Top 3.

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Author: David Fuller

David Fuller is OnAllCylinders' managing editor. During his 20-year career in the auto industry, he has covered a variety of races, shows, and industry events and has authored articles for multiple magazines. He has also partnered with mainstream and trade publications on a wide range of editorial projects. In 2012, he helped establish OnAllCylinders, where he enjoys covering all facets of hot rodding and racing.