We have known about the Hemi or HEMI V8 engines trademarked by Chrysler for a long time, but where does this engine come from?
The Hemi gets its name from the hemispherical cylinder head. Chrysler has been using Hemi since 1949, but this type of combustion chamber engine appeared much earlier, in the early 1900s. In Europe, it first debuted in the F1 cars of Fiat, Peugeot and Alfa Romeo. In America, it was introduced in the 1904 4-L model of Welch Motor Car Co. and was intended to replace side-valve engines. The advantages of hemispherical cylinder head engines in a nutshell: The air does not have to change direction in the combustion chamber, so the airflow is better. The engine, due to better flushing of the combustion chamber, fewer hotspots develop, thus increasing the lifespan of the engines. Due to its design, higher compression can be achieved, which provides more power. A Hemi has two large valves, which are opened with a pushrod.
But nothing is free in life. Let’s look at the disadvantages:
Due to the hemispherical design, it can only have two valves, otherwise the valves would open together, which would lead to the immediate failure of the engine. It is structurally more complex than flathead ones. This means higher manufacturing costs and more difficult maintenance. It can only be tuned to one rpm range, in contrast to today’s VVTI engines. It is optimized for either low or high rpms. In the case of a sports car, its disadvantage is that it is 25% heavier than an engine with a wedge-shaped combustion chamber. Now close your eyes and imagine the throaty roar of a Hemi engine at full throttle. That unmistakable sound—a symphony of power and aggression—has become synonymous with American muscle cars.
Many people associate the Hemi only with big American irons, and more educated (or not?) with Chrysler, but in reality many more European brands used the hemispherical cylinder head than American ones. Without claiming to be exhaustive, here are a few examples:
Alfa Romeo: Busso V6 – No, not the 24 valve one, but the original one!
Aston Martin: DOHC V8 – Yes, 5.3L, 4 camshafts, from the late 60s to the 80s
BMW: M10 – 2002 sports sedan: 2l, 4 cylinders, HEMI
Jaguar: XK – 1949-1992, from Le Mans winning D-Type, through E-Type to XJ6, familiar?
Lamborhini: V12 – Since 1963, every Lambo V12 is a hemi, for over 50 years
Lancia: V4/V6 – Low cylinder angle (10°-20°) V engines, Fulvia coupe? First DOHC? HEMI!
Lotus: Lotus – Ford Twin Cam – 1962 Lotus Elan, only for a few years though
Mercedes: M102 – 1.8L-2.5L almost all! Here’s the exception: 2.3 16V Cossie, a.k.a. DTM 190E
MG: MGA Twin-Cam – Only for 2 years, not the most reliable, but Hemi!
Mitsubishi: 4G1,4G5/4D5, 4G3 – early 70s, 3 engine families from the land of the rising sun
Nissan: Z, VG – In a million+1 cars
Porsche: 911 – from 1964 to 1999, i.e. ALL air-cooled 911s are HEMI
Toyota: V6/V8 – from the 1960s to the 90s most of their longitudinally mounted V engines were hemi
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