"Ya got a Hemi in that?" That is the question posed by a slack yawed yokel to the proud possessor of a shiny new Chrysler product in a series of advertisements. The smug reply from the Chrysler product owner is, "Yeah, its got a Hemi." And then he zooms off in satisfied automotive bliss. The implication is that a Hemi is a good thing, it makes your car more powerful, and ownership of a Hemi entitles you to an elevated level of respect from less worthy cars and their owners.
The name Hemi is closely associated with Chrysler dating back to the 1950's and today that association is being exploited in an advertising campaign that promotes Daimler-Chrysler's newest V8 engine sold in their largest US-made cars and many trucks. The campaign is working, even with the rapid rise in gasoline prices Chrysler is selling Hemi-equipped trucks and Magnum/Charger cars (based upon Daimler-Chrysler's parent Mercedes E-class sedan) at a brisk pace without the need for rebates or discounts.
The name Hemi is a shortening of the word hemisphere, which refers to a round object. In the case of the Hemi engine, the combustion chamber of each cylinder is hemispherically shaped. Imagine that the top 1/8th of a tennis ball was sliced off and that will give you the basic shape of the combustion chamber. The shape of the combustion chamber, along with the design of the cylinder head that each combustion chamber is contained within, are influential upon the engine's ability to burn the air and fuel mixture efficiency. And as we know, increased efficiency in the engine increases power and economy.
Chrysler in the 1950's promoted itself as "The Engineer's Choice" and pioneered many technical innovations, including torsion bar suspension, push button automatic transmission and the Hemi engine. The original Hemi was a 5.7-liter pushrod V8 that was an immediate success on the track and was a favorite amongst the Hot Rod crowd. But the cost per unit to produce the original Hemi and limited appeal with the general public caused Chrysler to drop the original Hemi by 1960.
By 1964 the importance of NASCAR racing success as a marketing tool was too powerful for Chrysler's managers to ignore and they rushed a 7-liter version of the Hemi into production in time to capture the Daytona 500 with a 1-2-3 win in February 1965. This solidified the Hemi mystique and through the Muscle Car era the Chrysler Hemi was revered for its power. Other engines in the Chrysler line made more torque but the Hemi was the top power champ, which added to the allure. But by the early 1970's the gas guzzling big cars from Chrysler had fallen far out of favor, the company tilted on the brink of receivership and the Hemi and its big cars got dropped in favor of smaller cars engineered by Volkswagen and Mitsubishi.
Time passes, Chrysler survives, and with an infusion of cash from new partner Daimler-Benz the Hemi name is revived. An all new design of a pushrod operated V8 with 5.7-liters of displacement, the new Hemi appears to be a consumer favorite and the Hot Rod crowd seems to be impressed as well. As the after market develops performance enhancers for the new hemi, you can expect to see it adapted for use in performance cars.
So what is special about the new Hemi engine? A pushrod design, there is nothing innovative about that. It uses electronic fuel and ignition control, but you would be hard pressed to find an engine sold today that does not have them. Duel spark plugs per cylinder help to burn the air/fuel mixture cleanly, but aircraft engines and racing engines had this back in the 1930's. So that hemispherical combustion camber shape must be the deciding factor.
Well actually, no. Other manufacturers have caught on to the design and have a hemispherical combustion chamber shape. My 1987 Honda Civic CRX engine has hemispherical combustion chambers, and nearly all modern engines have a variation on that design. While it may be cool to have an engine with the Hemi label, nearly all car engines today have that feature. So if you are asked if you have a Hemi in there, you can say "Sure."