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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 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 .
Chrysler developed its first experimental hemi engine for the Republic P-47 Thunderbolt fighter aircraft. The XIV-2220 was an inverted V16 rated at 2,500 hp (1,860 kW). The P-47 was already in production with a Pratt & Whitney radial engine when the XIV-2220 flew successfully in trials in 1945 as a possible upgrade, but the war was winding down and it did not go into production.
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 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 has hemispherical combustion chambers with V-shaped hanging valves controlled by the bottom-mounted camshaft via tappets, pushrods, and rocker's arms. Additional pushrods across the cylinder head and a second rocker arm on each actuate the exhaust valves.
Chrysler created its V-8 Firepower engine for the 1951 model year, using hemispherical combustion chambers. It featured 331.1 CID and produced an impressive 180 hp at 4000 rpm [ 39 ] While the name "Firepower" is no longer used, the name " Hemi " is still synonymous with Chrysler as a trademarked name for its engines, although they no longer ...