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Home/Technical Info/ Shelby and Cobra/
2.0 Shelby Cobras - the History and Development

The Ads for the first Cobra were quite simple, but the car was dramatically good looking.
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by Auto History Preservation Society Staff, Reprint With Permission Only

History and Development

Before Carroll Shelby came along, AC Cars had been using the smooth, refined Bristol straight-6 engine in its vehicles, including its AC Ace 2-seater roadster. This engine was a pre-WW design by BMW, which had be produced under license and then acquired by Bristol. However, by the 1960s the company knew the design was outdated. In 1961, Bristol decided to cease production of this engine and to move to Chrysler 313 cu. in. V8 engines. As a result, AC started using the 2.6 liter Ford Zephyr V6 in all of its cars.

In September 1961, Carroll Shelby sent AC a letter asking them if they would build a car modified to accept a V8 engine for him. Shelby contacted AC because he had previously had a positive experience with British-American hybrids, having raced an J-2 Allard which could be fitted with Oldsmobile, Cadillac, and Chrysler V-8s and which proved quite successful. Shelby liked the AC because it was simple, light (an aluminum body was fitted, and it had a reputation for being sturdy. AC agreed, provided a suitable engine could be found.

Shelby first went to Chevrolet to see if they would provide him with engines, but they declined, not wanting to add competition to their Corvette, which, at the time was involved in a "back door" factory racing program. Shelby then contacted Ford who was looking for a way to come up with a car that could compete with the Corvette. And as a matter of chance, they happened to have a brand new thin-wall small block engine which would be perfect for the light-weight AC.

The engine Ford suggested was Ford's 260 cu. In. Hi-Po engine - a new lightweight, thin-wall cast small-block V8 tuned for high performance. (The engine would grow to 289 cu. in when it was fitted in the Mustang).

In January 1962, mechanics at AC Cars in Surrey, England fitted the prototype chassis, number CSX2000 with a 221 cu. in. Ford V8, which had the same exterior dimensions. After testing and modification, the engine and transmission were removed and the engineless chassis was air-freighted to Caroll Shelby in Los Angeles on February 2, 1962. There, it was fitted with a 260 engine and transmission in less than eight hours and taken out on test. It was named right after the successful drive, and later Carroll Shelby claimed the name "Cobra" came to him in a dream.

Production proved to be easy, since AC had already made most of the modifications needed for the small block V8 when they installed the 2.6 liter Ford Zephyr V6 engine, which, surprisingly was of similar size and weight. This included reworking the AC Ace's front suspension.

But the most important modification was the fitting of a stronger rear differential to handle the power of the Ford V8. AC chose a Salisbury 4HU unit with in-board disk brakes for the prototype. It was fitted to reduce unsprung weight. This unit was the same as used on the Jaguar E-Type, where it handled the power of modified Jag engines just fine. On the production versions, the inboard brakes were moved outboard to reduce cost.

The only modification of the front end of the prototype Cobra from that of the AC Ace 2.6 was the mounting of the steering box, which was moved outward to clear the wider V8 motor.

The First Cobras (Mark I and II)

The first 75 Cobra Mark Is (including the prototype) were fitted with the 260 cu. in engine. The remaining 51 Mark I models were fitted with the famous 289 cu. in. V8, making them Mark IIs. At the end of 1962, AC completed a major design change of the car's front end. They were able to fit the car with rack and pinion steering, while still using the somewhat archaic transverse leaf spring suspension.

The steering rack was borrowed from the MGB while the new steering column came from the VW Beetle. The new car, known as Mark II, went into production in early 1963. About 528 Mark II Cobras were produced from 1963 until the summer of 1965, however, the last US-bound Mark II was produced in November of 1964.

But while the car was an immediate succcess, by 1964 the leaf spring Cobra began to falter in racing as it was competing with Corvettes and Ferraris, whos had either larger or more powerful engines. Shelby attempted to fit a big-block Ford "FE" series engine which came in 390 and 427 cu in. flavors at the time.

A 390 version was fitted, but it weighed over 100 lbs, more than the 289 and it unbalanced the car. Ken Miles drove and raced the FE powered Mark II car and said that the car was virtually undrivable, naming it "The Turd". Carroll realized that a new chassis was needed. This new chassis would be designated the Mark III.

Shelby AC Cobra (Mark III) "427 Cobra"

The new car was designed in cooperation with Ford in Detroit, who had gotten a taste of the success of beating GM's Corvette. It is said that this fueled Henry Ford II's desire to have a world class car and led to his rebuff when he tried to buy Ferrari. As such, no expense would be spared in the preparation of the new chassis.

This resulted in a totally new chassis which featured 4" main chassis tubes (instead of 3") and coil spring suspension all around. The new car also had wide fenders and a larger radiator opening. For all intents and purpose, this car was a special Ford racing chassis with an AC aluminum body formed around it.

The Mark III was powered by the famed "side-oiler" Ford 427 high performance engine. This engine had made a reputation for Ford in NASCAR and drag racing. For advertising purposes, it was under-rated at 425 HP and it pushed the standard Cobra to a top speed of 163 mph. A 485 HP (NASCAR-based 427) version was fitted in the competition model and it could hit a top speed of 180 mph.

Mark III production began on January 1, 1965, but two prototypes had been sent to the United States in October of 1964, where they exceeded all expectations in testing. Under the new deal with AC, cars were sent to the US as an unpainted rolling chassis, and here they would be finished in Shelby's LA workshop. Although an impressive automobile, the car did not sell well, due to its high retail price - driven up by the cost of the 427.

In an attempt to stimulate sales, some MK III chassis were fitted with Ford's 428 cu. in. passenger car engine. It had a longer strokeand a smaller bore to reach similar dimesions to the 427, but it was no race piece. It was primarily intended for road use rather than racing, though, in a few years, it wouild become famous in the "Cobra-Jet" Mustang.

A total of 300 mark III cars were sent to Shelby during the years 1965 and 1966, including the competition version. At the same time, and under a licensing agreement, 27 small block, narrow fender versions, called the "AC 289", were sold in Europe.

Production glitches and cost issues delayed the delivery of the number of vehicles delivered and as a result, the MK III missed homologation for the 1965 racing season and could not be raced by the Shelby team. However, it was raced successfully by many privateers. The success of this car was legendary as it went on to win races all the way into the 70's. Thirty-one unsold competition version Cobrass were detuned and made road worthy. They were renamed "S/C" for semi-competition. These are the rarest and the most valuable Cobra models and can sell for in excess of one million dollars.

Cobras in Racing

AC Cobras had an extensive racing career. Shelby wanted it to be a "Corvette-Beater", and since it weighed 500 lbs. less than the Corvette, it did just that. An AC Cobra Coupe was calculated to have done 185 mph on England's famous M1 motorway in 1964, driven by Jack Sears and Peter Bolton during shakedown tests prior to that year's Le Mans 24hour race.

Although extremely successful in racing, The AC Cobra was not a big financial success. That,and the fact that Ford wanted to brand special versions of the Mustang with the "Cobra" moniker, spelled its demise. These two events led Carroll Shelby to discontinue importing AC cars from England in 1967. Under the licnesing agreement, AC kept producing the coil spring Mark III AC Roadster with narrow fenders and a small-block Ford 289. As mentioned, AC called the car the "AC 289". It was built and sold in Europe until 1969.

Later Cobras

AC went on building cars, but it went into bankruptcy in the late 1970's. The company's tooling and eventually the right to use the name, were acquired by Autocraft, a Cobra parts reseller and replica car manufacturer. Autocraft was manufacturing an AC 289 V8 equipped "continuation car" called the "Mark IV". Carroll Shelby eventually filed suit against AC Cars in U.S. District Court in Los Angeles. The ensuing settlement resulted in Shelby and Autocraft issuing a joint press release whereby Autocraft acknowledged that Carroll Shelby was (and still is) the manufacturer of record of all the AC Cobras in the United States.

Cobra Coupes

In an effort to improve top speed along the legendary Mulsanne Straight at the 24 Hours of Le Mans race, a number of enclosed, coupes were constructed using the older leaf spring chassis and running gear of the Cobra Mark II. The most famous and numerous of these were the official works Shelby Daytona Cobra Coupes, which used Peter Brock's bodywork designs. Six were constructed in total, each being subtly different from the rest.

AC also produced a single Le Mans coupe. This car was a one-off and was nearly destroyed after a high-speed tire blow-out at the 1964 Le Mans race. It has now been completely rebuilt and now sits in private hands in England. The third significant Cobra-based coupe was the Willment Cobra Coupe built by the JWA racing team.

Mike Mc Cluskey of Torrance California, who is considered one of the premier Cobra restorers in the world, builds an exact replica of the racing Shelby Daytona Coupe. These cars are exact reproductions of the originals.

Another road-going Shelby Daytona Cobra replica is manufactured by Superformance and Factory Five Racing, a well known kit car company. These cars use the original Peter Brock design, but scaled up slightly to increase room inside. They also have a newly designed space-frame chassis. They are powered by Jack Roush-built Ford engines. The Superformance Shelby Daytona Coupe is the only modern-day vehicle recognized by Shelby as a successor to the original Coupes.

Super Snake

Shelby Motors built 22 427 competition roadsters. In 1965, one was converted into a special model. Carroll wanted to build the "Cobra to End All Cobras". The first one, number CSX 3015, was to be part of a European promotional tour before its conversion. This conversion called for making the original racing model street legal with mufflers, a windshield and bumpers, with some things left as originally fitted to the competition cars, including the racing rear end, brakes and headers.

Additionally, this car received twin Paxton superchargers, which gave the car nearly 800 HP and 462 lbs. ft. of torque at a low of 2800 rpm. Officially rated to be able to do0-to-60 in 4.5 seconds, legend says it could really hit 60 mph in a little over 3 seconds if one feathered the throttle to get traction off the line.

Another non-competition 427 roadster, CSX 3303, was converted to Super Snake level and given to Shelby's close friend, Bill Cosby. Cosby attempted to drive the super-fast Cobra, but had trouble keeping it under control. Cosby gave the car back to Shelby, who then shipped it out to one of their dealers in San Francisco, S&C Ford. S&C Ford sold it to Tony Maxey. But Maxey could not drive it safely either, and he lost control and drove it off of a cliff, landing in the Pacific Ocean. It was speculated that Maxey's accident may have been suicide. 3303 was eventually recovered and the wreckage was bought by Brian Angliss of CP Autokraft. He is expected to restore and auction this version.

Continuation Cars

Shelby's company Shelby Automobiles, Inc. once again began to manufacture the Shelby Cobra 289, FIA 289 and 427 S/C vehicles at its facility in Las Vegas, Nevada. These cars retain the style and appearance of their original 1960s ancestors, but are fitted with modern amenities.

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 were called the CSX 1000 and CSX 7500 Series, respectively. In February 2004 the first handcrafted aluminum body shell was built. The cooperative venture failed in 2006, and Shelby took over the production of a few cars.

Shelby's Cobra

Shelby's original model, CSX 3015, was kept as a personal car; and he sometimes entered it into local races like the Turismos Visitadores, a Cannonball-Run like race in Nevada.

CSX 3015 was auctioned off on January 22, 2007 at the Barrett-Jackson Collector Car Event in Scottsdale, Arizona for $5 million plus commission. In fact, the car was incorrectly nicknamed the "Super Snake" at the Barrett-Jackson auction. In reality, the car was usually referred to as "Carroll's Cobra" or the "Cobra to End All Cobras". "Super Snake" was stolen from the only truely named "Super Snake" which was a 1967 GT500 which was specially built with a medium riser 427.

The car is distinctive in looks as it had a unique triple stripe. This had been built to do demonstrations for the new Goodyear Thunderbolt tire. That car survives and should be referred to as the true original Super Snake.

Click on any Images If Below
to See them Full Size

Cobra MK I


Cobra MK II "Sebring". The results from this car's success, resulted in the two LeMans entries.

Cobra MK II.

Cobra MK III

Cobra MK IV

This is an early ad for the first (260 V8) Cobra - with 'ole Shell driving it hisself.

Cobras competed at Lemans in their first full year, albeit with a fiberglass roof.

Shelby experimented with a hybrid Cooper-Cobra but quickly abandoned it.

A much more successful car was the rebodied "Daytona Coupes".

In 1965 the Ford-engineered chassis was developed to house the 427 "side-oiler". This became the Corvette killer.










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