Chrysler Hemi Power 2 of 5

Chrysler built only 16 examples of a fuel-injected 392 Hemi for the 1958 300D, and 15 of them were quietly retrofitted back to carburetors within the same model year. That’s just one chapter in a decade where Chrysler’s FirePower Hemi and DeSoto’s own separate Hemi family kept leapfrogging each other in displacement and horsepower. Read on to find out how a 331-cubic-inch engine grew into some of the most powerful production V8s of the 1950s.

Sixteen of one experimental engine were built for the 1958 Chrysler 300D. Fifteen of them didn’t stay experimental for long. Chrysler had strapped an early electronic fuel injection system onto its most powerful Hemi yet, chasing a horsepower figure no carbureted engine of the era could touch, only to watch reliability problems force nearly the entire run back onto carburetors within the same model year. It’s one of the stranger footnotes in a decade where Chrysler and DeSoto were racing each other, and everyone else, toward bigger displacement almost every single year.

Where FirePower Started

Chrysler’s original FirePower Hemi displaced 331 cubic inches, built with a 3.815-inch bore and a 3.625-inch stroke, and remained in production from 1951 through 1955. Early versions produced 180 brake horsepower through a two-barrel Carter carburetor, though by 1955 the Chrysler C-300 upgraded to dual Carter WCFB four-barrel carburetors, extracting considerably more performance from the same basic architecture. The 331 remained Chrysler’s only Hemi engine offering until the 1956 model year.

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354 Cubic Inches and a Horsepower Milestone

The 1956 model year brought the 354-cubic-inch Hemi, sharing the 331’s 3.625-inch stroke but growing the bore to 3.9375 inches. In the Chrysler 300B, the standard 354 produced 340 brake horsepower, while an optional higher-output version reached 355 horsepower, making it the first production engine built in North America to exceed one horsepower per cubic inch of displacement. The New Yorker and Imperial received a tamer 280-horsepower version of the same 354, and it’s worth noting that every horsepower figure from this era through 1971 used the SAE gross measurement standard rather than the more conservative net figures adopted industry-wide starting in 1972.

A Truck Engine Wearing a Muscle Car’s Heart

The 354 didn’t stay confined to passenger cars. Chrysler’s heaviest-duty trucks used a variant marketed as the PowerGiant engine, available with one, two, or four-barrel carburetor setups from 1957 through 1959 on the company’s most demanding pickup applications. For 1956, the 354 also powered the New Yorker, Chrysler 300B, Custom, and Crown, and by 1957 it had spread to the Dodge D-301 and the “C” series pickups as well, with some versions using hybrid polyspheric cylinder heads rather than a true Hemi design, lighter in weight and blending characteristics of both head designs.

The 392 Raised-Deck Arrives

Chrysler significantly reworked the Hemi formula for 1957 with the 392-cubic-inch raised-deck engine, using a 4.00-inch bore and a 3.906-inch stroke on a taller block, with a deck height of 10.87 inches, roughly half an inch taller than the previous 331 and 354 blocks. Despite the redesigned architecture, the new cylinder heads were wide enough to still accept earlier intake manifold designs, easing the engineering transition even as the displacement and output climbed.

Two Tunes, Then a Dual-Quad Option

For 1958, Chrysler offered two single four-barrel versions of the 392: a lower-compression 9.25:1 variant producing 325 brake horsepower, and a higher 10:1 compression version delivering 345 brake horsepower. Buyers of the 1957 and 1958 Chrysler 300C and 300D could also step up to an optional dual four-barrel carburetor setup, pushing output to 375 brake horsepower, making the 392 one of the most powerful American production engines available anywhere at the time.

An Experimental Fuel-Injected 392

The rarest 392 variant of all used a little-known Bendix “Electrojector” electronic fuel injection system, available for 1958 only, capable of producing 390 brake horsepower. The system suffered from reliability problems tied to its underdeveloped computer control unit for the injectors, and as a result, 15 of the 16 Chrysler 300D units originally built with Electrojector were retrofitted back to carburetors. Despite that brief and troubled production run, 392 Hemis in general earned a reputation among drag racers as extremely dependable and powerful, with many remaining competitive well into the 1970s.

Racing Success Before the Muscle Car Era Had a Name

The Chrysler 300 letter series that carried these Hemi engines built its reputation partly on the racetrack rather than the showroom floor. The C-300, powered by the dual-carburetor 331 Hemi, proved dominant in NASCAR competition during the mid-1950s, winning a substantial share of the season’s races and helping establish Chrysler’s reputation for building genuinely fast, well-engineered performance cars years before the term “muscle car” entered common use. That early competition success gave the letter-series cars credibility that carried forward as the Hemi grew from 331 to 354 to 392 cubic inches over the following seasons.

DeSoto Built Its Own Hemi, Too

While Chrysler pushed the FirePower name, DeSoto’s engineers developed a completely separate Hemi family starting with a 290.8-cubic-inch engine in 1955, built with a 3.72-inch bore. By 1956, the same basic design grew to 329.9 cubic inches, keeping the same 3.72-inch bore but stretching the stroke to 3.80 inches, which required raising the block to accommodate the longer stroke. The range-topping Adventurer got its own bored-out 341-cubic-inch version of that same Hemi, good for 320 horsepower using a special hydraulic camshaft, 9.51:1 compression, and dual Carter WCFB four-barrel carburetors, while the 329.9-cubic-inch version carried on in the lesser Firedome and Fireflite models.

DeSoto’s Final Push

For 1957, the Adventurer’s Hemi grew once more to 344.6 cubic inches, keeping the same compression ratio but extending the stroke to 3.80 inches, now matching the bore exactly, and using the same carburetor setup as the previous year to produce 345 horsepower. That engine represented the final significant expansion of DeSoto’s independent Hemi program, a parallel development effort that rarely gets the same recognition as Chrysler’s own FirePower line despite pushing very similar numbers year over year. Both engine families were eventually phased out in favor of Chrysler’s simpler, cheaper-to-manufacture wedge-head big blocks, but the original Hemi’s reputation for strength and outright power never really faded, which is exactly why Chrysler brought the Hemi name back decades later for a new generation of V8 engines built on entirely different architecture. The original hemispherical-head engines from this period, whether badged Chrysler, DeSoto, or Dodge, remain some of the most collectible American V8s of the 1950s precisely because of how quickly the displacement and output climbed year after year, giving each model year its own distinct place in the story.

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