The real story about the 1966 F1 season

In 1966, a new 3 litre formula was created. It proved to be a transitional year for most teams. While Ferrari and BRM struggled with their new engines —and Lotus struggled just to find a reliable powerplant— the big winner was the Brabham team, which took victory two years in a row with the stock-derived Repco unit. With no more than 310bhp, the Repco was by far the least powerful of the new 3 litre engines but unlike the others it was frugal, light and compact[1]. Also unlike the others it was reliable and Jack Brabham, the 1959 and 1960 World Champion, won his third title in 1966 and became the first and only driver to win the Formula One World Championship in a car that carried his own name. (cf Surtees, Hill and Fittipaldi)

BRM built a new H 16 engine (3.0 litres) but in the 1966 season BRM used two cars: the P83 with the newly build BRM H16 (3.0L) engine and the P261 with the V8 (1.9L).
The new P83 was difficult to handle and unreliable so BRM decided to use the P261 in this season too. The best result for BRM was in Monaco where Jackie Stewart won in a BRM P261 and Graham Hill finished 3rd in his P83.

The Lotus 43 was designed for the 1966 season by Colin Chapman. The 1966 season was the first season where 3 litre engines were permitted. As a result, Chapman and Lotus made a deal for use of BRM's new H 16 engine as well as using new, wider tyres better able to put the power of the engine down on to the track.
The engine on paper was technically advanced and powerful, and Chapman had hopes that it would power his cars to another successful season. Alas, it was not to be. The first sign of trouble was when the new engine arrived and it required four men to lift it from the truck. The engine proved to be overweight, unreliable and was unable to produce the promised power. Jim Clark didn't score any points until mid season. Clark was able to turn his fortunes around and won the American GP at Watkins Glen at the end of the season, thereby winning the H 16's only race. In 1967 the 43 made its final start in the South African GP at the Kyalami circuit, where Clark again retired the car. The 43 chassis was an excellent design let down by a poor powerplant, and Chapman was left to rue his choice as he had been offered Repco engines for 1966, which went on to take the world championship that year for Brabham.

In the early days of the 3-liter engine formula, Maserati-powered Coopers would win the '66 Mexican Grand Prix in the hands of John Surtees, and their final victory would be achieved with Pedro Rodriguez at the wheel, at the 1967 South African Grand Prix.

Development of an all-new engine and chassis for the 1966 season began immediately after Honda's break-through F1 victory in Mexico. Having considered both V12 and V16 layouts to meet the new 3-litre regulations, Honda's engineers opted for the 12-cylinder alternative.
Once again the engine boasted more power than its rivals but the new machine was handicapped by being considerably overweight. Despite this Ginther ran second on its debut in Italy until a tyre burst and was looking good for a comfortable third in America before gearbox gremlins prevented a podium finish.

The Eagle T1G, powered by an obsolete Climax engine debuted at the 1966 Belgian Grand Prix and scored its first points with a fifth place three weeks later at the French Grand Prix.

Ferrari developed the Tipo 312 for the new Formula 1. Victories in 1966: Belgian Grand Prix in Spa (driver: John  Surtees from England) as well as Italian Grand Prix in Monza (driver: Lodovico Scarfiotti from Italy).