You don’t have to be much of a car enthusiast to know there is something special about the word “Hemi”. It’s a term widely used in the car business and has been for several decades -in almost reverent terms at times. But exactly what is a Hemi and what’s all the fuss about? To answer that question, let’s step back a few years and visit Chrysler in the 1940s.
In the late 1940s, WWII had ended and everyone wanted a car –especially powerful, fast ones. To meet this demand, Chrysler introduced not just its first V8 engine but engines with unique cylinder head designs. Unlike other previous designs, these new engines had combustion chambers that were cast round in the shape of a dome, or “hemisphere”. This hemispherical design allowed engineers to place the intake and exhaust valves on opposite sides of the combustion chamber. This lent itself to large valve surfaces and robust head cooling passages, all of which made for a much cooler running, more powerful engine.
During the 1950s and 60s, demand ramped up even higher and Chrysler Corporation made a lot of Hemis. Models such as Chrysler (with the FirePower Engine), DeSoto (with the FireDome Engine), Dodge (with the Red Ram Engine) all had Hemi engines. And, with fuel costs at historic lows, the automotive public just loved their new, powerful cars. When researching this article we spoke to the guys at Hoover Chrysler Jeep Dodge Summerville and they told us that in 1964 the stock Chrysler 426 HEMI Engine was actually so powerful that it was banned from NASCAR races as “unfair competition”, yet you could buy one to drive to work!
However, good things sometimes come to an end before their time and the Hemi engine is one example. Here’s why: the downside to the traditional Hemi design was complexity. From the beginning, Hemi engines had two rocker shafts per head and a complicated valve train. While this lent itself to engines that delivered superior performance, it also cost Chrysler more money to make them. Unfortunately, this would set the stage for the phasing out of the original Hemi engine design and reinstatement of the original, cheaper wedge head designs.
Today, we see many vehicles that bear the Hemi designation but in many cases this is a branding play. While some of today’s Hemis have real hemispherical heads, most have polyspherical heads (which are close to being Hemis) or are simply wedge heads. “Not that there is anything wrong with that”. Wedge head engines can be designed to be quite powerful in their own right and many manufacturers make them today with great success.