In 1965, the Fédération Internationale de l'Automobile, that administered Formula One racing, agreed to raise the series' maximum engine capacity from 1.5 litres (92 cu in) to 3.0 litres (183 cu in) from 1966.

Up until that point, BRM was challenging at the top with Lotus, Cooper and Ferrari.

The H16's development was complicated by BRM's involvement in two further V12 designs and a 4.2 litre version of the H16 for Lotus to use at the 1966 Indianapolis 500.

[6][7] The initial 32 valve engine produced 390 brake horsepower (290 kW) at 10,250 RPM, with a later 64 valve variant raising this to 420 brake horsepower (310 kW) at 10,500 RPM.

While these constituted reasonable figures compared to the Ferrari, Honda and Weslake V12s and the Cosworth V8 of 1967, the H16 had an extremely narrow power band and was by some distance the heaviest engine on the grid, starting out weighing 555 pounds (252 kg) when introduced in 1966 with the final lightweight version lowering this to 398 pounds (181 kg).