The History and Use of the Hemi | Autance

Almost no other name in the automotive world carries as much weight as the “Hemi” moniker does.

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The History and Use of the Hemi | Autance © The History and Use of the Hemi | Autance

Almost no other name in the automotive world carries as much weight as the “Hemi” moniker does. No other engines have led to more broken hearts on the dragstrip, more Bud Light cans tossed at NASCAR events or more speeding tickets than the Hemi.* But the engine we know as the Hemi today isn’t actually the same as the ones that the name was built on. 

The original engines used a special combustion chamber shape that allowed for more complete burning of fuel and air, but modern technology has changed all of that. Why should you care about Hemis, even if you’d never get caught dead at an oval rack? Car Autance’ editors don’t have mullets—yet—but we’re here to tell why you should care and why the word Hemi should be part of your vocabulary going forward.

*Probably. Just go with it.

What Is A Hemi And Where Did It Come From

The name “Hemi” refers to an engine with hemispherical combustion chambers. You’ll see the title on engines used in Chryslers, Dodges, and Ram trucks these days, but none of those companies created the engine design, nor are they the only ones to have used it.

The “Hemi” was originally created around the turn of the twentieth century by a person named Allie Ray Welch, who lived in Chelsea, Wisconsin. The first prototype was built by Truscott Launch and Engine Company and was a two-cylinder mill meant for use in a boat.

It wasn’t until decades later, in 1950, that Chrysler got around to dropping a Hemi into its cars. But even then, the engines weren’t called “Hemi. They went by several names, depending on the brand, including FirePower for Chrysler and Imperial, FireDome for DeSoto, and Red Ram for Dodge. The Hemi name appeared later and got its start in NASCAR.

Over the years, the Hemi has gone through various displacements, bores, strokes, and cylinder counts. Today, you can find a Hemi under the hoods of everything from Jeeps to Dodge Challengers, but they’re not the same engines that the name was built on. 

The new engines no longer have a hemispherical head, but the upside is that they’re being built to both produce and withstand massive amounts of power and torque, and are more fuel-efficient than ever before.

How Does A Hemi Work? 

In a Hemi, the top of the combustion chamber has a hemispherical shape, which means it’s sort of a rounded half-sphere. In these engines, the spark plugs are usually located at the top of the chamber and the valves are located on either side.

This shape and design offer many advantages:

  • The lower surface area in the combustion chamber relative to its volume allows less heat to escape and higher peak pressure.
  • The Hemi shape allows for larger valves, which improves airflow.

Of course, there’s no such thing as a perfect engine. The Hemi design has a few issues, most notably the inability to run four valves per cylinder. Street cars typically use four valves because the setup improves airflow, but the classic Hemi combustion chamber shape does not allow for that. Keep in mind that new engines that we know as “Hemi” don’t actually have the hemispherical combustion chamber shape.

Car Autance’s Glossary for Hemi 

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Combustion Chamber

The combustion chamber is the part of an engine where the air and fuel mixture is ignited by the spark plug. This ignition is actually kind of a small explosion that helps move the engine’s parts and power the vehicle.


Valves work to promote or retard the flow of fuel to and from the combustion chamber.

Spark Plug

Spark plugs create the spark that ignites air and fuel inside the combustion chamber. They do this with an arc of electricity that flows across the end of the plug.

The Car Autance Questionnaire on Hemis

Car Autance answers all your burning questions!

Q: Are Hemis Expensive To Buy?

A: If we’re talking about an original engine, the answer is yes—very. Even modern crate Hemis are expensive because of their power output and desirability. The good news is that buying a new Dodge, Ram, or Jeep with a Hemi isn’t the most expensive idea in the world, and will come with a warranty in case you decide to actually use the engine to its fullest potential.

Q: Why Aren’t Modern Vehicles Using Real Hemis?

A: Engine technology has evolved to the point that achieving the best power, fuel economy, and reliability requires a different engine design. There’s nothing wrong with modern Hemis. They’re just not real Hemis.

Q: I Don’t See Dodge In NASCAR Anymore. Is It Because Of The Hemi?

A: The Hemi was banned from NASCAR because it was just too good at helping Dodge win races. That meant that the Dodge Charger Daytona could no longer compete. Today, Dodge isn’t a part of NASCAR for many reasons, probably having to do with money, sponsorships, and the ability to field a competent team of drivers, mechanics, and race managers.

Video on Hemi

For all you kinesthetic learners out there, Car Autance brought you a video from one of our favorite and most trusted, sources. You’re welcome.

Car Autance’s Favorite Hemi Related Products

Car Autance’ editors can’t help you track down the right Hemi for your car, but we can get you started on your project with the tools to keep it running smoothly. They include the DeWalt Tool Set, Pro-Lift Jack Stands, and Mechanix Work Gloves.

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