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A hemispherical head ("hemi-head") gives an efficient combustion chamber with minimal heat loss to the head, and allows for two large valves.However, a hemi-head usually allows no more than two valves per cylinder due to the difficulty in arranging the valve gear for four valves at diverging angles, and these large valves are necessarily heavier than those in a multi-valve engine of similar ...
The Hemi-6 is a pushrod O.H.V. (overhead valve engine), with combustion chambers comprising about 35% of the top of the globe. This creates what is known as a low hemispherical shaped chamber. In this way, the "Hemi" moniker was used for the same kind of marketing cachet as Chrysler's 1950s-1970s Hemi V8 engines.
The engine's name is an acronym for either Compound Valve-angle Hemispherical or Canted Valve Hemispherical, where "Hemispherical" describes the shape of the combustion chamber. [ 1 ] [ 2 ] The CVH was introduced in 1980 in the third generation European Escort and in 1981 in the first generation North American Escort .
Fitted to the Maserati 250F Grand Prix cars, this engine won eight Grand Prix between 1954 and 1960 and the F1 World Championship in 1957 driven by Juan Manuel Fangio. The engine featured hemispherical combustion chambers fed by a Lucas indirect fuel injection system, a new development for Italian car manufacturers. Maserati subsequently moved ...
The cylinder head has four hemispherical combustion chambers, each with two valves having an included angle of slightly over 73°, with the exhaust valves being inclined from the horizontal about 4° more than the intakes. The valves are made of nimonic steel, and have double valve springs. The camshafts are hollow, and run in five bearings each.
The 90 degree V8 engine has a cast iron block, a short, stiff, dynamically balanced crankshaft carried on five bearings, light-alloy heads [3] with part-hemispherical combustion chambers, and two push-rod operated overhead valves per cylinder operated by a single chain-driven camshaft positioned centrally high up in the vee. [13]
In 1942-43, a range of configurations was considered and it was concluded that, for good breathing and high brake mean effective pressure (BMEP), the new engines would need vee-opposed valves operating in hemispherical combustion chambers. Two configurations of this type were selected for comparison in 1943 and the prototypes named "XG" and "XF".
The V family engine was used in the prestigious Toyota Century. Toyota had worked with Yamaha to produce the first Japanese full aluminum alloy block engine. The V family is often referred to as the "Toyota Hemi" [citation needed] as the engine features a cylinder head design with approximately hemispherical combustion chambers.