Chrysler Hemi Engine Advertisement from 1951Old Hemi Engine Advertisement

Even when Chrysler products suffered in build quality, MoPar engines were noted for their bulletproof reliability and durability as well as their often blistering performance. Undoubtedly, Chrysler's best known high-performance engine is the "hemi", introduced in 1951 as Chrysler's answer to the new Cadillac and Oldsmobile V8s introduced in 1949. The hemi engine was designed using Chrysler's experience in developing a 2,500-horsepower V16 engine for the P-47 fighter. World War II ended before the engine could be produced. After the war, Chrysler worked with Continental Motors in developing the air-cooled, V12 engine used in the M-47 Patton tank. Both used hemi-head engine designs.

The hemi got its name from its hemispherical combustion chamber with the intake and exhaust valves angled rather than side-by-side with the sparkplug near the center. Introduced in 1951, the Chrysler Firepower V8 displaced 331 cid, like the Cadillac V8, but produced 180 horsepower, 20 more than the Cadillac. The hemi's better volumetric efficiency allowed it to breath better for more power. The big disadvantage is the location of the valves meaning more complex rocker arm geometry requiring two rocker arm shafts in each cylinder head. Besides being more expensive to build, it took up more space under the hood.

Desoto and Dodge had their versions of hemi, the 276 cid Firedome in 1952 and 241 cid Red Ram in 1953, respectively. Built through 1958, the hemis got several displacement increases to keep Chrysler competitive, and often the leader, in the horsepower race.

By 1959, the hemi was replaced by the wedge head engine. With its wedge shape combustion chamber, it was less expensive to build and could make almost as much horsepower per cid. For example, the 392 cid hemi used in 1958 Chrysler 300D produced 380 horsepower, the same amount as 413 cid wedge used in the 1959 300E. The wedge head engine was built in a wide number of displacements - 350, 361, 383, 400, 413, 440 and cid - and was used in all MoPar brands.

The most potent were the Max Wedges that debuted in 1962 in the 420-horsepower 413 Max Wedge. Subsequently, their was the 426 version in 1963, the 440 Max Wedge in 1966, 375 horsepower 440 Magnum in 1967 and in 1969 the 440 Six Pack with its six barrel carburetors. The last of these Chrysler big-block engines were built in 1978.

Chrysler reintroduced the hemi in 1964 as the 426 Hemi. The 426 Hemi bore no resemblance to the earlier hemi. Basically, it used a top-end modification of the wedge engine. Called the "elephant engine" because of large size, it was initially produced for NASCAR racing with a minimum number offered to public to meet homologation requirements. From 1965 to 1971 it was available in a number of Mopar muscle cars, and even a few "family" sedans. Rated at a very a conservative 425 horsepower in "street" hemi form, tuners got as much a 800 horsepower from the 426 Hemi.

When several builders of high performance, cars needed more horsepower, they looked to the Chrysler hemi V8, either the original or second generation 426 hemi, and the equally capable wedge V8s. These included race-oriented Allards and Cunninghams, expensive sport coupes from Bristol and Jensen, and mega-buck grand touring cars like Facel-Vegas, Dual Ghias and Monteverdis.

Incidentally, the Chrysler HEMI V8s don't really have a truly hemispherical combustion chamber is not. It is flatter and more complex than the 1950s through 1970s Hemi V8's chamber.

Dodge and Plymouth Hemi-powered muscle cars produced during the 1960s and 1970s are now coveted collectibles with megabuck price tags. Cars like the Dodge Charger, Challenger and Daytona as well as the Plymouth Hemi 'Cuda, Superbird and Roadrunner with 426 Hemis and 440 Six Packs exchange hands for high six figure prices.