The GT40 project grew from Henry Ford II's desire to beat Ferrari at Le Mans after failed acquisition talks with Enzo Ferrari in 1963. Ford licensed technology from Lola Cars and its GT prototype, recruited Eric Broadley and ex-Aston Martin team manager John Wyer, and established Ford Advanced Vehicles in Slough to build the car. The first chassis was delivered on 16 March 1964. Production models were powered by a 289 cubic inch (4.7-litre) Ford V8, the same engine used in the Mustang, replacing earlier 255 cubic inch aluminium V8 prototypes.
The name "GT40" reflected the car's height of exactly 40 inches at the top of the windscreen, the minimum permitted under the regulations. Around 31 Mk I cars were built at Slough in near-race trim, with minimal concessions to road use. More than 50 were made during 1965, allowing the FIA to homologate the model as a Group 4 Sports Car for the 1966 through 1971 seasons.
The Mk I debuted at the 1964 Nürburgring 1000 km, retiring with suspension failure after holding second place early in the event. At the 1964 24 Hours of Le Mans, all three entries retired. After a season of disappointments under John Wyer, the programme was handed to Carroll Shelby's operation at the end of 1964.
Shelby scored immediately: Ken Miles and Lloyd Ruby won the 1965 Daytona 2000 km, and Ken Miles and Bruce McLaren finished second overall (first in prototype class) at the 1965 Sebring 12 Hours. However, the team again failed to finish at Le Mans in 1965, and the season as a whole was a disappointment.
While the heavier-engined Mk II dominated as a factory prototype in 1966, the Mk I — now homologated in the 5.0-litre sports car class — was raced by private customers and factory-supported teams throughout the 1966 and 1967 World Sportscar Championship seasons. The Mk I proved competitive in the sports car category, scoring championship points for Ford alongside the Mk II's prototype class victories.
Following the FIA's 1967 rule change limiting prototypes to 3.0 litres, the Mk I received a new lease of life. The John Wyer Automotive team, running under Gulf Oil sponsorship, upgraded the original 4.7-litre engine to 4.942 litres with approved modifications and refurbished the old chassis. With purpose-built 3-litre prototypes proving fragile and unreliable, the old Mk Is outran everything.
At the 1968 24 Hours of Le Mans, Pedro Rodriguez and Lucien Bianchi drove chassis GT40P/1075 to overall victory, the lone surviving Gulf-Wyer GT40 beating the best Porsche 907 by a clear margin. The engine in that car was a Windsor 302 cubic inch (4.9-litre) V8 producing approximately 425 horsepower at 6,000 rpm, fed by four 2-barrel Weber carburettors.
In 1969, the same chassis GT40P/1075 won again, this time driven by Jacky Ickx and Jackie Oliver. The victory margin was razor-thin: Ickx famously protested the unsafe traditional Le Mans sprint start by walking to his car and properly fastening his seatbelts, falling well behind at the start. The two men traded the lead with a Porsche 908 through the night, eventually winning by just a few seconds when the Porsche's drivers chose not to change worn brake pads near the end of the race. It was a victory as much of nerve as machinery.
The GT40 Mk I's story is among the most celebrated in endurance racing history. From near-failure in 1964 to four Le Mans victories — two as the factory's big-block weapon alongside the Mk II and Mk IV, and two more as an aging privateer entry that outlasted a new generation of cars — the Mk I demonstrated exceptional longevity and adaptability. Chassis GT40P/1075, winner of both the 1968 and 1969 Le Mans races, is one of the most significant competition cars ever built. The Mk I's survival into 1969, five years after its debut, remains almost without parallel in the history of international prototype racing.