1969 Ford Mustang Boss 429 Fastback a Fascinating Muscle Car

The Mind-Blowing 1969 Ford Mustang Boss 429 Fastback is one of the most fascinating Ford Muscle Cars of all time.

1969 Ford Mustang Boss 429 Fastback White Side

1969 Ford Mustang Boss 429 Fastback White


The 1969 Ford Mustang Boss 429 Fastback is one of the rarest and desirable Ford Mustang models ever produced. The Boss 429 engine was developed by Fords to compete with the powerful Mopar 426 Hemi in NASCAR racing. However, in 1969 to homologate an engine to race in NASCAR they required a minimum of 500 engines to be installed in production cars and sold to the public. Ford decided to install these very special and powerful engines in the Mustang. Producing very special production cars with a racing engine.

A mean aggressive look, limited production numbers, and the Ford race bread engine makes the boss one of the most sought out collectible Muscle Cars.

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Design of the Boss Cars

Design of the Iconic Boss Mustang cars was entrusted to Larry Shinoda. Ford wanted special cars to install the big 429 engines and the 302 to compete with the Z28 Camaro in Trans Am Racing. Shinoda came up with a simple but a mean look for the Boss cars compared to some of the other Mustang models of the same year. Externally the only thing that would make the Boss cars stand out from a standard Mustang was the wider tires, black chin spoiler, Boss Decal on the fenders and the massive fully functional hood scoop. He named the cars Boss as in honor of Ford president Bunkie Knudsen because he always called him “Boss”.

To save money Ford modified the standard 428 Cobra Jet Mustang body shells for the Boss 429 Models. They sent the bodies to Kar Kraft in Michigan to make the necessary modifications to fit the massive big block engine. Inner fender where extended, the radiator cradle was reinforced, the shock towers and firewall were modified. The control arm’s pivot point was lowered, and they also lowered the ride height. The battery was moved to the trunk due to the limited space. All Boss 429 cars came with a manual transmission. No AC was available due to size restriction in the engine bay.

1969 Ford Mustang Boss 429 Fastback A

1969 Ford Mustang Boss 429 Fastback

The Exterior

Except for the large hood scoop and the Boss decals externally the 1969 Ford Mustang Boss 429 Fastback looked like a standard Cobra Jet Mustang. In 69 the available exterior colors were Black Jade, Candy Apple Red, Raven Black, Royal Maroon and Wimbledon White. The hood scoop was painted body color on all the 1969 cars, on the 1970 models it was painted black.


1969 Ford Mustang Boss 429 Fastback Exterior colors:

  • Raven Black
  • Royal Maroon
  • Black Jade
  • Candy Apple Red
  • Wimbledon White



1969 Ford Mustang Boss 429 Fastback Black Interior

1969 Ford Mustang Boss 429 Fastback Interior

The Mustang Boss 429 Interior

For 69 the Interior was only available in black vinyl. Like other mustangs the seating was laid-out in a 2+2 configuration with front high-back bucket seats. However, the rear seats did not fold-down like other Mustangs do to trunk mounted battery. A simulated woodgrain trim was optional.


1969 Ford Mustang Boss 429 Fastback Drivetrain

11969 Ford Mustang Boss 429 V8 Engine

11969 Ford Mustang Boss 429 Engine

The Powerful Boss 429 Engine

The Boss 429 engine, also known as “Boss 9” was based on Ford 385 cubic inch block. The cast iron 429 cubic-inch block uses forged connecting rods, forged pistons, forged steel crankshaft, 4-bolt mains, thicker main bearing bulkheads and different oiling system compared to the 385 blocks. The bore was 4.36-inch with a 3.59-inch stroke with a compression ratio of 11.7:1.
Ford developed special aluminum heads with crescent hemispherical combustion chamber, massive square ports and staggered valves. The heads used 2.28-inch diameter intake and 1.9-inch diameter exhaust valves. The engine used no head gasket, each cylinder, water, and oil passage used individual O rings to seal the head to the block.

Ford Build 3 variations of the Boss 9 engine for the production cars. The Code S engines were used in early 1969 cars, code T engines in mid 1969 and code A engines were used in the 1970 models. The S code engines used hydraulic lifters. The T code engines used hydraulic lifters also, but Ford lightened up the rotating mass to make the engine rev up quicker. The hydraulic lifters in the S and T code engine limited the engines redline because above 5,800 rpm’s the lifter would start pumping air. And so, Ford Changed to solid lifters in the code A engines, allowing the engine to rev much higher.

The early “Boss 9” code S and T engines used a mild camshaft with 282-degree duration and .050-inch lift. This also limited the engines redline. On the A code engine ford switched to 300-degree duration cam with solid lifters and stiffer springs. This also helped raise RPMs and horsepower.

The engine came with an aluminum dual plane intake manifold and was topped by a quite small 735 cfm Holley carburetor. This carburetor was even smaller than the one installed on the Boss 302 engines. This was Fords other way to limit the performance and horsepower of the engine on the road cars.

The Ford “Boss 9” Engine

  • 429 cubic-inch V8.
  • 4.36-inch Bore with a 3.59-inch stroke.
  • 11.7:1 compression ratio.
  • Cast iron block.
  • Forged pistons.
  • 4-bolt mains.
  • Forged connecting rods.
  • Forged steel crankshaft.
  • Aluminum heads.
  • Crescent hemispherical combustion chamber.
  • Massive square ports.
  • Staggered valves.
  • 2.28-inch diameter intake valves.
  • 1.9-inch diameter exhaust valves.
  • Oil cooler.
  • The hydraulic lifters.
  • 282-degree duration and .050-inch lift Camshaft.
  • Aluminum dual plane intake manifold
  • 735 cfm Holley carburetor.


1969 Ford Mustang Boss 429 Fastback Side Red

1969 Ford Mustang Boss 429 Fastback Side

The Ford Boss 429 Engine Horsepower

The listed power rating was only 375 horsepower and 450 lb.-ft of torque. But, this was just Fords way of hiding the true potential of the engine due to legal issues and the rising Insurance costs. However, the production Boss 9’s true horsepower was well over 500 horsepower and some even claim that it was closer to 600HP. And so, to prove these claims engines were removed from new cars and Dyno tested and in later years engines were rebuilt to factory specs and tested. However, exact output numbers varied do to different testing parameters.

The engine’s true potential could be easily extracted by changing the restrictive carburetor, mild cam, and installing solid lifters on the S and T code engines. This would let the engine breath allowed it to reach it’s true 9000 RPM redline and horsepower potential.



The Boss 429 cars were only available with a close ratio Toploader 4 speed manual transmission.

1969 Ford Mustang Boss 429 Fastback Transmission Gear Ratios

  • 1st Gear – 2.32:1
  • 2nd Gear – 1.69:1
  • 3rd Gear – 1.29:1
  • 4th Gear – 1:1


1969 Ford Mustang Boss 429 Fastback Ad

1969 Ford Mustang Boss 429 Fastback Ad

The Mustang Boss 429 Differential

The standard rear differential was the bulletproof Ford 9-inch Axle, with Traction-Lok and a 3.91:1 gear ratio. Also available as an option was a 4.30:1 gear ratio with a Detroit Locker.


1969 Ford Mustang Boss 429 Fastback Body/Chassis

The Ford Mustang utilizes a Unibody or unitized body design, a one-piece frame and body structure. This type of structure is designed to be lighter and more rigid than a standard body and frame configurations.



To fit the bigger engine Ford needed to make some serious modifications to the Mustang’s front suspension. They lowered the ride height and dropped the pivot point on the control arms. They moved the shock towers and changed the front suspension geometry. A ¾ inch sway bar was added to the rear, and stiffer spring and shocks were used.
The modified suspension, wider rims and tires resulted in lower and wider track which greatly improved the Mustangs road handling. Even with the heavier engine up front the “Boss 9” cars were one of the best handling Mustangs of the 69-model year.



The independent front suspension contains shorter upper and longer lower control arms with ball joint connections. The Heavy-Duty coil springs are placed directly over the upper control arm. Vertically mounted hydraulic telescopic shock absorbers. Strut stabilizer arms that are mounted from the lower control arm to the frame and a Heavy-Duty sway bar helps reduce body roll.


Rear suspension contains a full Axle with 53-inch variable rate semielliptical leaf springs. Staggered mounted heavy-duty hydraulic telescopic shocks. And, A ¾ inch sway bar.


All 1969 Ford Mustang Boss 429 Fastback were equipped with power assisted brakes with 11.3-inch front discs and 10-inch rear drums.


Red 1969 Ford Mustang Boss 429 Fastback

Red 1969 Ford Mustang Boss 429 Fastback

1969 Ford Mustang Boss 429 Fastback Performance

The Boss 429 engine was engendered and developed for NASCAR racing and made power at higher RPMs. The restriction added by Ford to the road engines did not make for the quickest cars off the line. However, the cars were capable of speed up to 175mph on the open road.
Off the line performance of the early 69 cars was 0-60 mph in 7.1 seconds and the quarter mile in 14.09 seconds. With, some changes Ford improved the street performance to the later code T engine cars to 0-60 mph in 5.3 seconds and the quarter mile in 12.2 seconds.

However, simply replacing the small carburetor and some other Ford restrictions would release the engines true potential, allowing the Boss 9 Mustangs to become incredibly fast street machines.


Sales and Production of 1969 Ford Mustang Boss 429 Fastback

In 1969 there were 857 Boss 429 Mustangs built by Ford Motor Company. These 857 cars were given special NASCAR identification numbers that were placed on the driver’s door. Production began in 1968 at Kar Kraft’s assembly plant in Brighton, Michigan. The cars bodies were removed directly from the Ford’s Rouge assembly line and transported to the Kart Kraft plant to perform the necessary modifications to fit the big Boss 429 engine. These cars received special “KK” designation that stood for Kar Kraft. In 1969 the first Boss 429 produced was number KK1201 and the last in 1970 was number HH2558. 


The Boss 9 engine and NASCAR

Ford’s response to Chrysler high powered 426 Hemi being used in NASCAR was to developed the Boss 429 engines. To race this engine in NASCAR Grand National Division a total of 500 would need to be produced and sold in a production car. Ford decided to install these race engines in the Mustang instead of the bigger Torino that they were using to race in NASCAR.

1969 Ford Mustang Boss 429 Fastback Collectability

The low production numbers and the NASCAR developed 429 cubic inch engine makes the 1969 Mustang Boss 429 Fastback very desirable collector car. If you would like to own one of these cars they are not easy to find and if you do find one, they demand a big money and can sell for well over $300,000.00. An unrestored 69 sold for $417,000 Mecum in 2013. And, in 2016 at Barret-Jackson a fully restored 69 Boss 429 sold for $500,000.00.


Special Features of the 1969 Ford Mustang Boss 429 Fastback

  • 429 Cubic inch Engine
  • Engine oil cooler
  • Four-speed Top Loader transmission
  • 3.91:1 Traction-Lok 9” Differential
  • Trunk-mounted battery
  • Modified suspension
  • Lowered Ride Height
  • Front and rear stabilizer bars,
  • Polyglas F60X15s Tires
  • Quicker ratio power steering
  • Power front discs brakes.
  • 8000-RPM tach.
1969 Ford Mustang Boss 429 Fastback Rear Red

1969 Ford Mustang Boss 429 Fastback Rear


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