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Issue 07:04:04 - April 23, 2007

Featuring a super-performer: The 1969 Boss 429 Mustang

The 1969 Boss 429 Mustang is one of Ford’s most amazing muscle cars. Though the production models had a rocky start, it was a super-performer that really stood out in its day. Its appearance and power made it very appealing then and even more so today.

The Boss 429 Mustang beginnings can be traced back to early NASCAR races when Chrysler and Ford were running neck-in-neck to secure their racing victories. Chrysler had dominated the track with its 426 Hemi engine race cars. Ford wanted to counter this engine with a new big block engine of its own. So, the Boss 429 engine came into existence.

The Boss 429 V-8 engine was created from top to bottom as an all-racing engine. Of course, as with all race cars, NASCAR required that a minimum number of these be built as regular production cars. So, the Boss Mustang was chosen to fulfill this purpose. The engine was first tried out in the Blue Crescent, but the intake and exhaust ports located in the big alloy heads were too large. So, this attempt was called the “shotgun.”

Designing the 429 engine

The standard features on the massive 429 V-8 engine included large ports with big 2.3-inch inlet valves. These were the largest ever fitted on a production engine by Ford. The engine also had large alloy hemi heads, a strong cast-iron block with four-bolt main bearings, and crank and connecting rods that were both made of forged steel.

The timeframe for engine development was short because Ford had many other projects it was working on. So, Boss 429 Mustang production was contracted to a company called Kar Kraft in Brighton, Michigan in September 1968. Kar Kraft was already in the process of developing the Ford Trans-am Boss 302 race cars.

There were several obstacles that Kar Kraft engineers faced while creating the Boss 429 Mustang. One was the fact that the engine bay was more than two inches too narrow for the engine. To solve this problem, they did some major surgery and moved the entire suspension outward by a full inch on each side. As a result, new re-shaped shock towers, a wider strut tower brace and new top and bottom suspension arms were needed. Also, new heavy-duty springs and uprights had to be used. To fit appropriately with the big valve cover, a slimmer power brake booster was used. Also, the car’s battery had to be relocated to the trunk to allow for better weight distribution.

Heavy-duty springs, a thick rear stabilizer bar, and staggered shocks were all used to improve the rear suspension. The car was an inch lower than the usual stock Mustangs, so a unique, shorter spoiler was used to decorate the front.

Other engine features

The engine had a forged-steel crank as well as forged-steel connecting rods. It had four bolt mains and aluminum cylinder heads that had a modified Hemi-like combustion chamber called a “crescent.” The cylinder heads operated by the dry-deck method, using no head gaskets. Instead, each cylinder, water passage and oil passage had its own “O” ring for sealing purposes.

The car’s overall weight was 3,870 pounds, and it had an axle ratio of 3.91:1. A four-speed manual transmission was used. The car could accelerate from 0 to 30 mph in only 3.2 seconds, from 0 to 60 mph in only 7.1 seconds, and from 0 to 100 mph in only 13.6 seconds. Its top speed was 118 mph.

Testing the prototypes

The prototypes for the Boss 429 Mustang had to be put through extensive Ford testing. They were also required to pass the emission tests and the hot and cold environment running tests as well. This would let Ford know that the engine and its chassis were ready for any driving conditions. Therefore, the Boss 429 Mustang became a watered-down version of the race cars, having a horsepower rating of only 375 horsepower in the end. This was because of the use of a mild hydraulic camshaft, a smog pump, and a small carburetor.

Power unleashed

The Boss 429 Mustang was announced to the press, but many people were disappointed with its performance. A common observance was that it could barely beat a 428 Cobra Jet when it came to acceleration. It also had poor handling because of the large, heavy engine in the front. To help matters, Ford engineers went to work. They adjusted the camshaft from the mild hydraulic type to a hotter grind solid lifter. Also, the racing connecting rods were made to be more lightweight.

These changes helped to increase the engine horsepower rating to 400 horsepower; however, it was still labeled as 375 horsepower. The differential ratio was also dropped from 3.5 to 3.9, so the engine began to perform amazingly well.

Power was unleashed in the Boss 429 Mustang like one could never imagine, and it became an outstanding performer. Race cars powered with this engine began to dominate the NASCAR tracks for 1969. Unfortunately, Ford pulled out during the racing season, so the engine never reached its full potential.

Distinctive Boss 429 Mustang features

The Boss 429 Mustang had a number of unique features that separated it from the rest. Each one had “Boss 429” decals on the rear of their front fenders. Each one had a special NASCAR KK # tag on the inside of the driver’s door just above the Ford Warranty Plate. The “KK” and number stand for Kar Kraft production numbers. The first model was labeled as “KK NASCAR 1201” and the final 1969 model was “KK NASCAR 2059.” The final number for all Boss 429s was “KK NASCAR 2558.”

The Boss 429 models also had a hood-mounted air scoop that featured a unique intake flapper valve that could be controlled manually. Standard features on the models included deluxe interior with power steering, close ratio gearboxes, and low-ratio 3.9 Traction-Loc differentials. They also came with Magnum 500 wheels measuring 15 x 7. The wheels included extended centre caps. The interior for all 1969 Boss 429 Mustangs was the color Black. The exterior paint color options were Royal Maroon, Candy Apple Red, Black Jade, Raven Black, and Wimbledon White.

Production information

Production for the Boss 429 Mustang began in January 1969 at the Kar Kraft factory. The production Cobra Jet Mustangs were moved from the Dearborn plant to Kar Kraft and were turned into Boss 429 models. The total number produced for 1969 was 859 models. The Boss 429 “Shotgun” Mustangs were in high demand once the public found out about them, so Ford had to crank out another 500 models for 1970. Total production ended with 1359 models for 1969 and 1970.

The Boss 429 Mustang is a highly-coveted collector car today. Muscle car fans from all over share excitement when one of these is being displayed at a car show or museum. It was a truly a “boss” of the Muscle Car era.


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