Engine made by Fivet of France. Transmission by Transaxle (combined rear axle and gearbox). Two-seater and dickey or Sports two-seater. Optional 1327 cc engine pre war, standard post war.

AC 12 hp is a car model produced by the British car maker AC Cars .

The six-cylinder AC chassis followed the lines of its four-cylinder contemporary, featuring quarter-elliptic springing front and rear, a three-speed gearbox in unit with the rear axle and worm final drive. Front wheel brakes were optional at first, standard issue from 1927. Although the first sixes were running in 1919 it took some time to get production under way and the majority of ACs produced immediately after The Great War were powered by British Anzani engines. Rated at 12hp for taxation purposes, the four-cylinder AC remained in production until 1928, the firm relying exclusively on the Weller six thereafter. 

After the First World War manufacturers considered putting a two-cylinder boxer engine. But they decided to continue with the four-cylinder engines, and a few were equipped with motors from French Fivet . Then they went over to the English-made Anzani engines. AC ordered 2 000 engines at 1496 cubic centimeters. Price wise, the model was designed to be above the Morris Cowley model.

The two-and four-seater bodywork was considered one of the most beautiful small cars at the time. A sporty two-seater model was particularly appealing with the dropped rear and polished aluminum body. Anzani engines were around 25 horsepower, but for the sports model there was an tuned AC 12 hp engine up to 40 hp, and the model was called 12/40 .

AC 12 hp enjoyed success in competitions and made numerous record runs. In 1921 Harry Hawker ordered a special racing chassis to which he provided a low and slender body, made in his own aircraft factory, Hawker. With the car he drove half a mile, 805 meters flying start and achieved an average speed 169.2 km / h. In the Double Twelve Hour race at Brooklands in May 1922 a factory-built AC 12 hp car with a special sixteen-valve engine achieved a record for so-called light cars (with less than 1500 cubic centimeters displacement). They traveled 2750 km with average speed 114.63 km / h. AC 12 hp's participated in the 200 Miles Race for light cars but were not very successful in 1921 and 1922, as best saw a seventh place.

In November 1922, however, came a real breakthrough when JA Joyce became the first person with a light car running a speed over 100 mph, equivalent to 160.93 km / h. The car that had a streamlined Hawker-body, sixteen-valve engine and chassis where the rear axle was above the frame rails. The distance traveled was exactly 163.14 kilometers. Copies of this car, but with Anzani engines as standard, were on sale for £1000 up to 1926. However, it is unknown how many sold.

In 1923, the 1924 200 Mile Race competitions were also run in sixteen-valve engines factory cars. Joyce achieved a three position in 1923 and four in subsequent years. During the 1920s,there were changes in AC Cars management. SF Edge, formerly associated with Napier cars, took a seat on the board. He was known to be dynamic and controversial, so it was no surprise that he did not agree with the original members Weller and Portwine. They retired in September 1922 and handed over operations to Edge. He started production of four-cylinder engines Anzani model in Cubitt factory, and reneged on a deal for 2000 engines that AC Cars committed to purchasing from Anzani. At first, the four-cylinder cars sold well, but later in the decade, sales declined.

Although AC's reputation was established by John Weller's with the famous overhead-camshaft six, its early offerings relied on proprietary four-cylinder engines. AC's Weller-designed six entered production in 1922, helping to secure the marque's place in motoring history when in 1926 a 2.0-litre model driven by Victor Bruce and W J Burnell became the first British car to win the Monte Carlo Rally. Indeed, the company was then engaged in an active competition programme under the stewardship of that formidable motoring personality, S F Edge with the policy had already born fruit the previous year when an AC six broke the 24-hour world record for its class with a speed of 82mph.