The 429 is unquestionably one of the most sought after and valuable engines ever built.
The Ford 385 engine served as the inspiration for the Boss 429 engine. It was discovered that a Mustang’s body was not broad enough to accommodate a large Boss 429 engine, and as a result, Ford commissioned Kar Kraft of Dearborn, Michigan to modify existing 428 Cobra Jet Mach 1 Mustangs in order to make them suitable for use with the new Boss 429 engine. Kar Kraft made considerable modifications to the Mustang, including enlarging the shock towers and extending out the inner fenders, to accommodate this enormous engine and transmission combination. These vehicles also received a hood scoop that was operated by hand in addition to the hole that was created in the hood. A conservative estimate of the power and torque of these vehicles was 375 horsepower and 450 pounds-feet of torque. The actual power output was well in excess of 500 horsepower. A total of 375 manufacturers and dealers were named, primarily as a result of legal issues and increasing insurance costs.
There were a total of 1,358 Boss 429s manufactured. The Boss 429 is the result of collaboration between NASCAR and Chevrolet. For the Sprint Cup Series, Ford was attempting to design a Hemi engine that could compete with the Chrysler 426 Hemi, which was well-known at the time. According to NASCAR’s homologation requirements, at least 500 automobiles had to be equipped with this power train and sold to the general public before it could be considered legal. Ford decided that the Mustang would be the vehicle that would house this new engine after much deliberation and consideration.
Compared to other Mustangs of the era, both model years had a more subdued look, with the only outward identification coming in the form of stickers on the front fenders, immediately aft of the front tires. The rest of the automobile had a fairly clean appearance, which was in contrast to the majority of Mustangs that Ford had made.
They were given distinctive NASCAR identification that was placed on the driver’s side door to demonstrate exactly how remarkable these cars were to begin with. To distinguish each car, a “KK” number was assigned, which stood for Kar Kraft. KK #1201 was the very first Boss 429 ever built, and KK #2558 was the very last Boss 429 ever built.
Unfortunately, sales of the 1970 Boss 429 Mustangs began to dwindle, and as a result of rising production costs, rising gas prices, and other internal Ford concerns, it was decided that 1970 would be the final year for the Boss 429 Mustang.
At the present day, these automobiles are highly sought for. As of 2008, auctions on eBay and at Barrett-Jackson had fetched bids in excess of $350,000 per auction.
Model Year: 1969
Ford Motor Company produced 859 Boss 429s in 1969, which is a record number. In 1969, there were five distinct exterior colors to choose from Raven Black, Wimbledon White, Royal Maroon, Candy apple Red, and Black Jade, and the interior was only offered in one color. The hue of the hood scoop matched the color of the automobile. Because of the size of the engine, all of these vehicles were equipped with a manual transmission and did not have air conditioning as standard.
Model Year: 1970
Ford Motor Company produced 499 Boss 429s in 1970, a record number for the company. Interior colors were White or Black, with five new exterior colors Grabber Orange, Grabber Green, Grabber Blue, Calypso Coral and Pastel Blue. All of the hood scoops on this year’s models were painted black, regardless of the color of the vehicle. These automobiles were similarly equipped with a manual transmission and did not have air conditioning.
The combustion chamber architecture of the Boss 429, you could say, is its heart and soul: a conventional hemi layout with a twist. On a normal hemi engine, such as the one manufactured by Chrysler, the valves are deployed perpendicular to the crankshaft centerline, or vertically in this photograph’s orientation. However, the valves 2.28-in intake and 1.90-in exhaust were turned counterclockwise around 30 degrees on the Boss, mostly to enhance the port angles hence the term Twisted Hemi. Additionally, as seen here, there were typically two squish-quench zones on either side of the valves. Certain racing versions of the Boss head omit the compression pads, resulting in chambers with a more pure hemispherical shape. Except for early prototypes and a few unique nitro drag racing castings, all Boss heads are composed of aluminum.