The purest form of the most celebrated (and copied) automobile of all time is without question the original incarnation known as the 289, or leaf spring, MK1 Shelby Cobra. The brain-child of legendary race car driver Carroll Shelby, the story is often told of the British coachbuilder AC Cars, Ltd., being smoozed into providing car bodies for shipment to the U.S., and the installation of the potent high performance 289/305 horsepower engine by a group of "hotrodders" in Southern California. Almost more a fluke than by design, on one could have been more surprised than "ol Shel" himself when not only did it "go like stink," it bacame so instantly in demand that the original car had to be painted several different colours to uphold the illusion that Shelby American was indeed constructing cars for sale.

 There were 1,003 of the '60's vintage cars built, 655 of them were the 2000 series model. The early 2000 models came with a 260 V8 (75), which was later updated to the now famous 289.  The first cars were fitted with the 4.2-litre engine and the Borg-Warner 4 spd., gearbox, not long after a 4.7-litre unit was fitted. This boosted power from 165 to almost 200 bhp and a top speed of 140 mph. More stunning was the acceleration 0-60mph in just over 5 seconds. This was the first Cobra for Britain, introduced in 1964. 

 Development of the Shelby car had begun as early as 1961 at AC Cars in Britain. Under supervision of chief engineer designer Alan Turner of AC the chassis was stressed and strengthened to prepare it for the increase of horsepower and especially torque. Initially the regular 221 ci Ford unit was used for the prototype; remarkably this engine only weighed 7 kg more than the Bristol unit used before. The new Borg-Warner manual gearbox put on an additional 4.5 kg compared to the earlier Moss transmission, but in all the increase in weight of the V8 powered Ace was surprisingly limited.
In high performance trim the old Bristol unit produced about 150 hp; the new Ford engine was good for 240 hp but this didn't prove a problem for the car. What did however was the 365 Nm torque the new engine produced, next to upgrading the chassis and suspension it required a new Salisbury final drive, like the one used in the Jaguar E-type. Another feature of the prototype were the inboard disc brakes requested by Shelby; this idea was rapidly abandoned after the first prototype since the heat from the brakes melted the final drive's oil seals. Shelby had also requested a glassfibre body like on the Chevrolet Corvette but AC rejected that. Not only was the original aluminum body lighter (it was only 23 kg) than a glassfibre body would have been at the time, but AC also partly owned the sheet metal factory which supplied the aluminum for the body.
In 1962 the prototype, without its power train, was transported to Shelby in the US. On the exterior only minor revisions were visible, most notable were the flared wheel arches to fit the wider track of the suspension and the more protruding front end with narrower grill. Shelby fitted the prototype with a high-compression 260 ci engine version, which delivered an impressive 325 hp. Then he used it for car shows and road tests by journalists and alike, who where all blown away by the cars amazing performance. It topped 246 kph and accelerated from 0-60 mph (96 kph) in 4.2 seconds. To give the impression that the production of the car had already started it was resprayed in a different paint color each time it was taken for a test drive.
After generating enough publicity the car was taken into production that same year with the 260 ci engine producing 260 hp; the delivery of the cars initially got under way very slowly due to all sorts of engineering problems still needing to be solved. Sufficient cooling of the engine was the main problem and for a while Shelby even had to resort to fitting Corvette radiators since there was no suiting Ford radiator available.

At the end of 1962 it became clear that the Cobra still had some teething problems. Next to overheating there were complaints about lack of precision in the steering and even steering failures, a weak front suspension and less performance than advertised. That last problem was taken care of by introducing a 289 ci (4735 cc) version of the Ford Fairlane engine, which also included a new radiator, in the Cobra early in 1963. This engine produced 271 hp and 426 Nm torque and gave the car a performance closer to that of Shelby's original 260 ci High-Power test car, though it came still a few horsepower short. In the months that followed the inaccurate worm and sector steering was replaced by a modern rack and pinion steering system, the front suspension wishbones were strengthened, a wider grill and side vents were added to the body to solve the overheating problems and also the bootlid was shortened for more body rigidity and the flares at the wheel arches enlarged to fit wider tires. Other changes were improved electrics including an alternator, and a longer final drive (3.77:1 instead of 3.54:1) to reduce the 0-60 mph acceleration time.
Sometime in 1963 the improvements amounted to so much that the Cobra was a distinctly better car than before, and so it was referred to as the Mk II. Question is, when exactly did it become a Mk II? Was it when the 260 ci block was replaced by the 289 ci block after 75 Cobras had been completed in the first months of 1963 or was it when the Cobra had completed its first evolution after 125 were manufactured in June 1963? Fact is that starting with car number 126 the external features identified with the Mk II appeared, like the side vents. Since the distinction is a bit hazy, even more so by all the proper Mk I versions later more or less upgraded to Mk II specs, the Cobras lacking the external features of the Mk II and built between 1962 and 1963 usually are referred to as Mk I.
A "standard" Cobra 289 weighed only 984 kg and had a maximum speed of 222 kph. It accelerated from 0-60 mph (96 kph) in about 5.5 seconds and needed 1 litre of fuel every 6.5 km. To keep this little brute, it measured 3.85 x 1.55 x 1.24 m (length x width x height), on the road it had an independent front and rear suspension constructed out of lower wishbones, transverse leafspring upper links and telescopic dampers. Solid disc brakes in front and rear provided the stopping power. For those who wanted more an extensive list of performance options was available, like high compression cylinder heads, dual 4-barrel carbs (standard it had a single 4-barrel Holley) or even four 2-barrel Weber carbs.  With a 385 bhp 289 engine, the Cobra* made its racing debut in late '62 at Riverside Speedway, California with driver Billy Krause. In 1963, the Cobra* had its first significant racing victory at the National SCCA meet, taking first, second and third place to the Corvettes' 4/5/6.

This is a breakdown of the numbers with the 2000 Series Cobras

Leaf Spring Cobras:
260 ci engine Street Cars - 62
260 ci engine Factory Works racers - 4
260 ci engine Factory-prepared racers - 1
260 ci engine Independently-prepared racers - 7
260 ci engine Dragonsnake - 1
Total 260 ci engine production - 75
289 ci engine Street Cars - 453
289 ci engine Factory Works racers:
-Standard Competition - 2
-Sebring race cars - 3
-LeMans race cars - 2
-LeMans replica racers - 3
-427 Prototype Flip-Top - 1
-289 FIA cars - 5
-Daytona Coupes - 6
-USSRC Roadsters - 6
Total 289 ci Works race cars - 28

289 ci engine Factory-prepared competition cars:
-Standard Competition - 2
-LeMans prototype - 1
-LeMans replicas - 3
-USRRC roadsters - 5
Total Factory prepared competition cars - 11

289 ci engine Independently prepared competition cars - 21
289 ci engine Dragonsnakes - 4
289 ci engine bare chassis for Mercer Cobra - 1
289 ci engine Willment Racing Coupe - 1
289 ci engine COB/COX Street Cars - 59
289 ci engine COB/COX Race Cars - 2
Total 289 ci engine Cobra - 580

Total Leaf Spring Cobra 260 & 289 cars - 655

 

CSX Designations

CSX 2000
The original Cobras. All small block engines, slab side bodies, street cars. CXS2000 was the first Cobra built.

CSX 3000
Production started in 1965 and ended in 1967. These Cobras featured the Ford FE 427 or 428 big block engines.

CSX 4000
Production started in 1996 and continues through today. These Cobras are assembled in Las Vegas and are sold as component cars (less engine and transmission).

CSX 5000
The Carroll Shelby Series1 car, which featured a carbon fiber body and an aluminum chassis. There were powered by GM Oldsmobile engines.

CSX 6000
COB for cars sold in the UK, and COX for cars built for export.
All were powered by Ford small block engines and featured aluminum bodes.

CSX 7000
Production started in 1998 and continues through today. These Cobras are assembled in Las Vegas and are sold as FIA 289 series cars. They are based on the small block chassis, feature cut back doors and larger fender flares. These are component cars.

CSX 8000
Similar to the original CSX 2000 series cars. These are component cars.

CSX 9000
Cobra Daytona series. These are component cars.
  CSX1000                                                                                                                                                                                                                              Recent vintage aluminum roadsters offered by Shelby Autos. Originally claimed to be bodies and frames sourced from the "new" AC Cars company in UK. A very small quantity of these were sold, 13 according to Amy of SAI.

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