For 1966 the Formula One engine capacity limit was increased to 3.0 litres from the 1.5 litres of the previous five seasons. McLaren considered and discounted British Racing Motors (BRM), Maserati, Coventry Climax and Oldsmobile engines before opting for a Ford V8 engine. This engine was originally designed for the Indianapolis 500, the premier single-seater oval track race in the United States, and had to be reduced in capacity from 4.2 litres to the 3.0 litre limit. This choice was partly motivated by the belief that it might bring financial support from Ford, although this never materialised. Ex BMW and Daimler-Benz engineer Klaus von Rucker was initially appointed to carry out the conversion of the engine in England. However, progress was slow so the project was transferred to Traco Engineering in California, United States, where extensive modifications were made to the internals under the oversight of McLaren's Gary Knutson. In its 4.2 litre form the Ford engine produced 470 bhp and McLaren expected the reduced capacity version to produce about 335 bhp. In fact, it produced 300 bhp in a narrow power band and was further handicapped by its large size and weight; combined with the gearbox it weighed nearly as much as rival team Brabham's entire car. In order to allow time to further develop the Ford, McLaren also used a Serenissima M166 3.0 litre V8 engine for some of the races. This engine produced about 260 bhp and required modifications to be made to the monocoque but was at least relatively light and compact. Four- and five-speed ZF transaxle gearboxes and a Borg & Beck clutch were employed.