What Mopar Fans Need To Know About The Forgotten HEMI 235CI V-6

The legendary Chrysler Hemi engines are known for being high-output monster V-8s. From the 426 Street Hemi to the turbocharged Hellcat, these engines are under the hoods of the fastest cars any U.S. automaker has ever produced. To put it simply, Hemi is synonymous with American V-8 power and performance. Every Hemi engine of note has had eight cylinders, but buried deep in the annals of Mopar history, there have been various outliers with fewer pistons that bore the Hemi name.

Back at the dawn of the first-gen Hemi engines, Plymouth developed a Hemi V-6 that would have revolutionized the mid-performance segment. A cheaper and more fuel-efficient six-cylinder, with more power than typical V-8s, could have been a game-changer for the Chrysler division, but for reasons that have never been fully explained, it never went into production. With the Hurricane inline-six equipped Dodge Charger SIXPACK turning the page for Mopar performance, now is a good time to look back on the Hemi V-6 that never was.

In order to give you the most up-to-date and accurate information possible, the data used to compile this article was sourced from various manufacturer websites and other authoritative sources, including Hot Rod, William Weertman, and Automobile Catalog.

1951 Plymouth Hemi V-6

In 1951, Chrysler introduced the new FirePower series of engines that had unique hemispherical combustion chambers, giving them radically more horsepower and torque than conventional motors. At the time, these engines were not marketed as Hemis, but are now regarded as the first generation Hemi engines. Most of Chrysler’s divisions had their own version of the first-gen Hemi engine, with Dodge calling theirs the “Red Ram” and DeSoto the “FireDome.” Plymouth, however, didn’t have a Hemi of their own, and wouldn’t have one under the hoods of their cars until 1964, with the 426.

First-Gen Hemi Engines

Plymouth almost had a Hemi in 1951, because they developed a 235 cubic inch V-6 with hemispherical combustion chambers, known internally as the A173. The engine, designed by Chrysler’s Powerplant Research and Engine Design division, had dual overhead cams, and was part of an experiment that also developed an inline-six Hemi, as well as the Hemi V-8s that went into production. The development of the 235ci Hemi V-6 was reportedly far enough along that it was a viable engine, though there are no known examples of it being tested in a vehicle.

Hemi Replacement for the Flathead Six

The point of developing the 235ci V-6 was to take advantage of the Hemi’s superior performance and to replace the Plymouth Flathead Six. More importantly, it was meant to kick the butts of every single Ford V-8, so chances are it was an impressive powerplant. There are no dyno tests for the 235 Hemi, nor any published power stats, but an approximation can be had by looking at what it was designed to beat.

A 1951 331ci Flatthead straight-six was capable of generating a respectable-for-the-time 145 horsepower, while a ’51 Ford Flathead 255ci V-8 only unleashed a rather anemic 112 ponies. Even the Ford Flathead 337ci V-8 that was used primarily in trucks only made 152 horsepower, which is about what Chrysler was getting from its V-6 engines. It’s not hard to imagine that 235 Hemi V-6 was capable of producing in excess of 150 horsepower, similar to the output of the 241ci Red Ram Dodge Hemi V-8.

No Future for the 235 Hemi V-6

Unlike the Ball-Stud Hemi, another Chrysler engine that never made it into production, there is almost no information on the 1951 Plymouth Hemi V-6. There are no pictures of it, no cars equipped with it, and no surviving examples of it in a museum. The world probably wouldn’t even know of its existence if not for a brief footnote in former Mopar engineer William Weertman’s book Chrysler Engines, 1922-1998.

According to the guy who helped design Chrysler engines, including the 426 Hemi, for over 40 years, the 235 Hemi V-6 never went into production because the company considered it too risky to build an expensive new unconventional design. This explanation leaves much to be desired because Chrysler went ahead and put the rest of the Hemi line-up into production and those engines were every bit as expensive and unconventional. Whatever the case, this potentially killer engine was killed off.

Chrysler Hemi-6 Engine

While Plymouth and America would never get a V-6 Hemi, one popped up Down Under in the 1970s. In 1966, Chrysler restarted their project to develop a Hemi six-cylinder engine, this time to replace the Slant 6 in Dodge trucks. For unknown reasons, this second attempt didn’t pan out either. Meanwhile, Chrysler Australia wanted a new six-cylinder engine for the Australian Valiant models, so the American parent company sent them their prototype for further development. According to Hot Rod magazine, the Aussies nailed it and came up with an inline-six known as the Hemi-6 engine.

Hemi-6 Triple Threat

Working from the American prototype, engineers at Chrysler Australia was able to develop not just one, but three Hemi-6 variants. The entry-level 215ci engine produced a decent 139 horsepower and 199 pound-feet of torque. The mid-level bumped those power numbers up to 165 horsepower and 234 pound-feet of torque. Finally, the top dog 265ci made 203 horsepower and 262 pound-feet of torque in the standard version, while a high-performance variant cranked out 302 horsepower and 320 pound-feet of torque. The Hemi-6 engine was in production from 1970 through 1981.

A Valiant Effort

Chrysler Australia put these amazing Hemi-6 engines in their Australian Valiant models, including the Chrysler Valiant Charger. The Aussie exclusive A-body Valiant Charger is one of the coolest muscle cars that was never sold in the United States. Looking like a cross between a Dodge Charger and a Dart, the 1971 VH Valiant Charger R/T was available with the 302-horsepower Hemi-6 engine. It also had 318 and 340 V-8 options that produced significantly less horsepower than the Hemi inline-six. With a wider track than its American Dart cousin, it had a wide aggressive stance.

1971 Valiant Charger R/T Power and Performance

(Performance stats sourced from Automobile Catalog)

K-car Pseudo Hemi I-4

No discussion of Hemi variants would be complete without mentioning the most shameful chapter in Mopar history. Beginning in 1981, Chrysler began outfitting its K-car line-up with imported 2.6-liter inline-four Mitsubishi engines. There was nothing particularly wrong with the Japanese engine, but for some reason, Chrysler promoted them as Hemis and even badged their vehicles as such. Imagine how funny it must have been for a ’68 Charger R/T 426 Hemi owner to see a ’78 Aries pull up at the light with a “Hemi 2.6” fender badge. The weird thing is, these Mitsubishi engines did have hemispherical combustion chambers, but they were in no way legitimate Hemi engines.

Chrysler K-cars:

• Chrysler LeBaron (1981-1989)
• Dodge Aries (1981-1989)
• Dodge 400 (1982-1983)
• Dodge 600 (1984-1986)
• Plymouth Reliant (1981-1989)

K-car Crisis

The Hemi-powered Chrysler B-body cars of the classic era, like the Dodge Charger, Coronet, and Plymouth Road Runner were some of the coolest-looking, fastest rides ever made. The Chrysler K-cars of the late 1970s and 1980s were the complete opposite of that, being some of the dorkiest, low-performance vehicles ever churned out. Equipped with the 2.6-liter Mitsubishi Pseudo Hemi engine, these K-Cars did a 0-60 crawl in as long as 15 seconds. To put that into perspective, a Hemi-equipped ’71 Roadrunner could blaze a quarter-mile in 13.1 seconds.

Stolen Muscle Car Valor

As if it wasn’t already bad enough that Chrysler tried to pass an imported I-4 off as a Hemi engine, the K-car era also saw the company drag its proud muscle car legacy through the mud. From 1981-1987, the Charger nameplate returned as a “performance” package on the Dodge Omni, a front-wheel drive four-cylinder hatchback. Similarly, the Daytona name was defamed 1984 when it was applied to a hatchback with a 95-horsepower option. In 1978, Chrysler had the nerve to badge-engineer a Mitsubishi Galant as a Challenger, which undoubtedly prompted someone to brag that they had a Challenger with a Hemi in it.

The 235 Hemi V-6 Inspires Next-Gen Mopar Performance

Most people think, and rightly so, of the Hemi engine as a powerful V-8 under the hoods of the fastest cars, but it has been many different things over the years. The Hemi engine started as 2,500-horsepower V-16 for the P-47 Thunderbolt fighter aircraft and then was adapted as a V-12 for use in armored vehicles like the M47 Patton tank. The Hemi engine even saw use in the Chrysler Air Raid Siren, making an ear-splitting 138 decibels, the loudest ever made. Also, as shown here, Hemis have been made on a smaller scale in four- and six-cylinder configurations.

It’s a shame that the 1951 Plymouth Hemi V-6 never made it into production, because it really had a winning formula. A more fuel-efficient six-cylinder engine that produced similar horsepower to an eight-cylinder would have been a hit and could have added to the Hemi legacy. As the Australians showed, it is possible to pull impressive power out of a six-cylinder with Hemi architecture. It may have taken almost three-quarters of a century, but the Hemi V-6 has inspired Chrysler to develop a high-output six-cylinder with the Stellantis Hurricane twin turbo I-6 engine. Capable of making up to 550 horsepower, the Hurricane replaces the Hemi in most Chrysler-related vehicles.