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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 ...
In return, hemi head engines tend to have complex valve trains, are expensive to build, and both larger and heavier than conventional designs. A hemispherical combustion chamber is an efficient shape, with an excellent surface-to-volume ratio, minimal heat loss to the cylinder head, [clarify] and room for two large valves.
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.
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 .
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.
Using a pushrod overhead valve system kept down design, development and production costs and allowed Turner to base the design of the cylinder head on those he developed for Triumph motorcycles [6] [8] including the use of hemispherical combustion chambers. [9] Adapting the Triumph head design for use in a saloon car engine required much work ...
All T engines utilize a timing chain and have a cast iron block with an alloy cylinder head with hardened valve seats and a hemispherical combustion chamber design . All T engines are carburetted except those with electronic fuel injection, "E" designation. All T engines use a 2 valve OHV design except those with a DOHC performance head, "G ...
Simca do Brasil introduced a 148 cu in (2.4 L) version in May 1962 but the real surprise was the 150 cu in (2.5 L) "Emi-Sul" of April 1966. This engine has overhead valves and hemispherical combustion chambers; it produced 138 hp (103 kW) in its most powerful version. [20]