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CATEGORIES (articles) > Cars we emulate > Cobra > AC Cobra 427

AC Cobra 427

427 A/C Shelby America CSX 4109 Cobra Signature Series #3 of 4
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Shelby Cobra
Shelby Cobra redirects here. See also the Shelby Mustang Cobra

The AC Cobra was a powerful Anglo-American sports car built in the 1960s. It was far from the first car to combine a lightweight European chassis and aluminium body with a big American V8 engine, but it is possibly the most famous. The later, larger-engined cars are still among the highest-performing road vehicles ever sold.

Like many British specialist car manufacturers, AC Cars had been using the smooth, refined Bristol straight-6 engine in its small-volume production, including its AC Ace 2-seater roadster. Unfortunately for AC and other manufacturers, Bristol decided in 1961 to cease production of its engine and instead to use Ford V8 engines. Thus, AC had a car without a future source of power. Into this void stepped American ex-racing driver Carroll Shelby, who in September 1961 airmailed AC a proposal to ship its engineless cars to Shelby's California works to be fitted with American V8s. Shelby had previous experience with Anglo-American hybrids, having raced an Allard.

AC agreed, provided a suitable engine could be found. It was, in the form of Ford's 260 in³ HiPo (4.2 L) engine - a lightweight, thin-wall cast small-block V8 tuned for high performance. In early 1962, the first engineless AC Ace was air-freighted to Shelby's Los Angeles facility, where it was fitted with an engine and transmission in less than eight hours and taken out on test. Carroll Shelby claims the name "Cobra" came to him in a dream, and the car was given that name.

1999 AC Cobra 427

It proved to be a great performance success; the automobile had originally been designed by Shelby with the intention it would be a "Corvette-Beater" and at nearly a ton less than the Chevrolet Corvette, the lightweight car did just that. Production proved to be less easy; the AC chassis needed extensive work to take the Ford drivetrain, and at first, the cars were slow to be produced. Soon, a larger but similar Ford engine, the 289 in³ (4.7 L) V8 was fitted. Shelby Cobras began an extensive racing career with this engine, which boosted power from 165 to approximately 270 hp (123 to 201 kW) and gave it a new top speed of 140 mph (225 km/h).

1964 saw an even larger engine fitted; Ford's famed 427 in³ racing engine (7.0 L) developing 485 bhp (362 kW) and attaining a top speed of 163 mph (262 km/h). Even more extensive rework of the AC design was needed to accomplish this; the big-block FE-series engine was much too large to fit in the standard engine bay. The front tires were moved outward, with extended wheel-arches to cover them, and a new coil-spring suspension was designed.

Some Shelby Cobras were fitted with Ford's 428 in³ (7.0 L) engine, a less powerful engine despite the nominal increase in displacement, intended for road use rather than racing.

AC Cars stopped producing the Roadster platform on which the Cobra was built in 1968, at which point Shelby stopped producing Cobras. Decades later, after some of his lawsuits attempting to squash the manufacture and sale of Cobra replicas failed to win at court, Shelby announced that a small number of certified "real" Cobras would be built by special order through his company, Shelby Cars Ltd. As of 2006, they can still be ordered either devoid of a drivetrain or with the buyer's choice of a 289 in³ or 427 in³ V8.

AC Cobra
AC Cobra

The Cobra is probably the most cloned car in history; an astounding number of replica Cobras have been produced, to the extent that the originals are in a minority. Some are AC Cobra lookalikes, while others are perfect replicas in every detail. In some ways it could be argued that the best of the replicas are superior to the original, having the benefit of decades of engineering advances and refinement. In 2004, Sports Car International named this car number two on the list of Top Sports Cars of the 1960s.

Shelby worked with the Chrysler Corporation from 1989 to 1991 to help develop and style the Viper supercar and in the late 1990s, developed his own Series 1, a composite-bodied high performance car powered by the 4.0 L, DOHC, 32-valve V8 from the Oldsmobile Aurora luxury sedan producing 320 hp. A more powerful supercharged version was available in limited quantities as well. The Viper and Series 1 are alternately considered to be the succesors to the Cobra, although the Series 1 was/is more like the Cobra than the Viper is.

AC Cobra (2004-)

In 2003, Carroll Shelby International Inc. and AC Motor Holdings, Ltd. announced production of authentic Shelby/AC Cobra, with the production vehicle arriving at dealers in July 2004. Initially available models included Shelby AC 427 S/C Cobra and Shelby AC 289 FIA Cobra, which will be branded as the CSX 1000.


The 'production' AC MK V is sold without an engine or transmission. The buyer can choose options suggested by the distributor.

Suggested Specifications

Engine head Cast head Aluminium head
displacement 302ci (4949 cc), 351ci (5752 cc) 302ci (4949 cc), 342ci (5604 cc), 347ci (5686 cc)
horsepower 225-250 315-450
torque (lb-ft) 300-? 295-400
stroke (in), crank type 3-3.5 cast 3-3.4 cast, 3.4 forged
compression ratio 8.5-9 9-10

Specifications (USA)

The AC MK V runs on a fuel injected 5.0 L Ford V8 engine rated at 340 hp and 310 ft·lbf of torque at 3750 rpm, a 5-speed manual transmission, limited slip differential, 16 in wheels, leather interior, wool interior carpeting, carbon fiber body panels on a tubular steel chassis.

Cobra Clubs

Because of the popularity of the Cobra (authentic and replica) owners have started their own culture. There are Cobra Clubs around the country where enthusiasts meet and ride.

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CATEGORIES (articles) > Cars we emulate > Cobra > AC Cobra 427

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