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Media post: HEMI History


“Hey, does that thing have a Hemi?” Do you may remember this line? It’s from a notable Dodge TV commercial of a decade ago. If you haven’t seen the original commercial, head on over to YouTube and take a look -it’s pretty funny. The original commercial, along with several follow-up ones, were part of a highly successful advertising campaign for Chrysler and their Hemi trademark.

So, now that “Hemi” has become a household word, have you ever wondered exactly what a Hemi is? Is it real technology or is it just a marketing term? As it turns out, its a bit of both today. And thanks to the Service Department at Temecula Hyundai of Temecula, CA, a full service Hyundai dealer, we have the whole story for you.

The first Hemi

Chrysler introduced a new line of V8 engines in the early 1950s that had an unusual shape to their cylinder heads. Unlike previous heads, Chryslers had chambers that were cast in the shape of perfect domes, also known as a hemisphere. It wasn’t long before “hemisphere” became “hemi” and a new word was born. Later in the 50s, it became a brand name registered by Chrysler Corporation.

The perfect design

Today, the Hemi design is legendary. The dome-shaped combustion chamber allowed engineers to do something they could never do before; they had enough room inside the head to place the intake and exhaust valves opposite each other. In previous designs, engine valves were crowded next to each other. However, with hemispherical heads, the engineers could make the valves oppose each other. This allowed for nice large valve surfaces and large head cooling passages; both of which made for a much cooler running engine. And, because the engine was cooled better, higher compression ratios could be designed in, resulting in an engine that also produced superior horsepower and torque.

Yes, it was banned

Chrysler’s Hemi engines were built during the 1950s and 60s. During this time, they had models such as Chrysler (FirePower Hemi Engine), DeSoto (FireDome Hemi Engine), Dodge (Red Ram Hemi Engine). Because the cars were so powerful and with fuel costs at historic lows, the automotive public loved these powerful, Hemi-engined cars. When researching this article, we learned that in 1964, the Chrysler 426 HEMI Engine (the largest one built) was actually so powerful that it was banned from NASCAR races as “unfair competition”.

End of the line

The downside to the Hemi design was complexity. Because of the opposing valves, Hemi engines had to have two rocker shafts per head and a relatively complicated valve train. While this lent itself to powerful engines, it cost Chrysler more money to make them. Unfortunately, this would set the stage for the discontinuation of the original Hemi design and the debut of cheaper wedge-head designs.

The marketing department

Today there are a lot of vehicles that bear the Hemi designation but do they have really Hemi engines in them? Well, today no one makes a true hemi engine. While some of today’s engines have roughly opposing intake and exhaust valves, they don’t have the true hemispherical cylinder heads of a real Hemi engine. That doesn’t stop the Chrysler marketing department from using the label, though. You will see the Hemi designation on many Ram trucks today but they don’t have a real Hemi engine.

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