Carol Shelby and the Cobra

In 1962 AC was approached by Carroll Shelby to use a small block Ford V8 Motor in the Ace chassis, producing the AC Cobra. Shelby needed a car that could compete with the Chevrolet Corvette in US sports car racing. The resulting Cobra was a very powerful roadster, and it is commonly blamed for the introduction of the 70 mph (113 km/h) limit on British motorways. Although a major factor in the decision, after a coupe version was caught doing 196 mph (315 km/h) during a test run.[1] a recent spate of accidents in foggy conditions also helped the introduction of the limit.[2]
At the end of the 1964 racing season, the Cobra was being outclassed in sports car racing by Ferrari, Carroll Shelby decided he needed a bigger engine. A big block 390 Ford FE engine was installed in a Cobra and the result was scary, the car was virtually un-drivable. It was decided that a completely new chassis was needed. With the combined help of Ford’s computers and the experience of the AC engineers, the new MKIII was born with 4 inch (100 mm) main tubes instead of 3 inch (75 mm) for the chassis, huge cross-braced shock towers and coil springs all around and made the new AC Cobra MKIII an absolutely unbeatable 2,200 lb race car. The engine that was installed in the car was the famed Ford 427 engine FE NASCAR Side Oiler Ford V8 motor, a power-house engine developing 385 bhp in its mildest street version. Unfortunately, the car missed homologation for the 1965 season and was not raced by the Shelby team. However, it was raced successfully by many privateers and went on to win races all the way into the 1970s. The AC 427 Cobra, although a commercial failure when in production, is one of the most sought-after and copied automobile ever. It was produced in two versions, a street model with a tamer motor, optional dual carburetors, a glove box and exhaust running under the car and a competition version with a stripped interior, no glove box, different instrument layout and revised suspension. The competition version also had a more powerful motor with only one carburetor, side exhausts, a roll-bar and wider fenders to accommodate racing tires. At the end in 1966, Shelby was left with a 31 unsold competition cars and decided to sell them to the general public under the name of Cobra 427 S/C or Super Competition. (Today these S/C cars are the most sought after models and can sell in excess of a million and a half dollars).
Carroll Shelby sold the Cobra name to Ford in 1965 and went on to develop the famed racing Ford GT40.
Meanwhile AC went on producing a milder version of the 427 MK III Cobra for the European market fitted with the small block Ford motor. The car was called the AC 289 and 27 were produced.