Category: Hemi

What is a Hemi? – Dan Carney @DesignNews

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Have you spotted a Mopar hot rod and wondered, “That thang got a Hemi innit?

Chrysler vehicles have long been renowned for their Hemi V8 engines, which are legendary for their power and performance. Remember the silly “That thang got a Hemi innit?” commercials from the aughts, with the two goofball fanboys interrogating owners of new Dodge vehicles about their engine status?

Most people know that a Hemi means performance, but how many people actually know what “hemi” means? That’s why we’re here. “Hemi” is a reference to the engine’s combustion chamber shape. It is short for “semi-hemispherical,” which means that the combustion chamber space cast into the engine’s heads looks like it was carved out with an ice cream scoop.

“If you cut a ball in half, the rounded top is the combustion chamber shape,” explained Brandt Rosenbush, company historian for Chrysler, which is now part of a company called “Stellantis” following the merger of Fiat Chrysler Automobiles with Peugeot.

A semi-hemispherical combustion chamber has the minimal possible surface-area-to-volume ratio, so less energy is lost as heat through the combustion chamber’s surface, said Rosenbush. It also enjoys good volumetric efficiency because the dome combustion chamber shape provides ample room for large intake and exhaust valves.

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Twenty years ago, Chrysler unleashed a pandemonium of third-gen Hemi V-8s. Here’s how to tell them apart – Daniel Strohl @Hemmings

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While many cars and trucks of the Eighties and Nineties dispelled the notion that American performance died off with the original muscle cars, it took an entirely new engine—one more powerful and less expensive to produce than its predecessor—to reignite the horsepower wars and usher in a new golden age. The Hemi V-8 has since become a standard-bearer for Chrysler, Dodge, Ram, and Jeep vehicles, and its basic engine architecture has spawned more than a dozen configurations, some of them difficult to discern from others. For that reason, we’ve put together this spotters guide to the third-gen Hemi family of engines.

What sets the Hemi apart

Teased in the 2000 Chrysler 300 Hemi C and the 2001 Dodge Super8 Hemi, the new 5.7-liter Hemi (Chrysler stylizes it as HEMI, but for expediency’s sake, we will not) debuted in the 2003 Dodge Ram pickups, featuring a deep-skirt cross-bolted iron block, aluminum heads, overhead valves, 4.46-inch bore spacing, the same bellhousing bolt pattern as the Chrysler LA-series V-8s, coil-on-plug ignition, composite intake manifolds, multipoint fuel injection, and that controversial head design.

Early (2003-2008) 5.7L Hemi heads, top; Eagle heads, bottom

Like the second-generation 426 Hemi, the 5.7L Hemi heads featured opposed valves for a true crossflow design, twin spark plugs, and rocker shafts. The third-generation Hemi did not, however, feature a full hemispherical combustion chamber. Instead, Chrysler’s engineers decided to flatten either side of the combustion chamber to improve combustion efficiency and emissions.

Some might argue that doesn’t make the engines true Hemis, but then again, the Hemi V-8s of yore were massive, heavy engines that cost a lot to machine and that wouldn’t meet modern-day fuel-efficiency or emissions requirements.

*David Kimble cutaway illustration of the 5.7L truck engine.*

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VIDEO: Build a hemi in less than 10 minutes! – Dan Stoner @Hemmings

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WATCH THIS: Hemify your life

There are few things as satisfying as watching an old motor undergoing a fresh rebuild, amiright? There’s just something about a vintage cast-iron block and all those imperfections being perfected that warms an otherwise blackened gearhead heart. The aroma of assembly lube and fresh hi-temp paint, gasket sealer and metal polish…those are pleasures that mere mortals will die before ever experiencing.

And especially with an old mill like a ’51 – ’53 Chrysler 331-cu.in. V8: these early Hemi blocks were cast with their bellhousings, which makes them just a skosh more readily available, these days, than their later, bigger 392 cousins. Which also means there’s a better chance of you finding one and experiencing the sheer joy of owning, rebuilding and running your very own early Hemi. That’s just bucket-list stuff, right there.

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