What’s a Hemi?

My very first car as a kid in England was a 1946 Riley RME. I thought it was cool because it had a chrome grille like a ’34 Ford and it had a race-developed, twin-cam HEMI—whatever that was. Back then, there was no internet to look things up but a trip to the library revealed that the word HEMI was an abbreviation for hemispherical combustion chambers—whatever that was.

Believe it or not, HEMI-heads are nothing new and their history can be traced back to the early 1900s when they could be found in a number of European cars including the 1904 Welch Tourist, the Belgian Pipe of 1905, the 1907 Italian Fiat Grand Prix car, the French Grand Prix Peugeot of 1912 and the Italian Grand Prix Alfa Romeo of 1914—race-bred alright. However, it was the Welch design that became the blueprint for the many successors that included numerous motorcycle engines.

Where the HEMI-head differs from other cylinder head designs such as the “flathead” Ford which is known as an “L” head design, is that their combustion chambers are hemispherical or half-bowl-shaped compared to most chambers that resemble a flattened, double egg. The chamber operates in a cross-flow configuration where the air-fuel mixture flows in one side; the more-or-less centrally located spark plug ignites the mixture and the exhaust gases exit on the opposite side from the inlet.

The use of a HEMI-head became prevalent in motorcycle engines because not only was it efficient, but it was not an overly complicated assembly in a single-cylinder application where the pushrods ran up the outside of the cylinder. Incidentally, a HEMI-head can be used with a pushrod, SOHC or DOHC valve train.

Believe it or not, HEMI-heads are nothing new and their history can be traced back to the early 1900s when they could be found in a number of European cars…

The concept even worked well in early air-cooled, radial airplane engines that are more-or-less a number of single cylinders arranged in a circle around a common crankshaft. In fact, by 1921 the U.S. Navy had announced it would only order aircraft fitted with air-cooled radials.

Obviously, World War II propelled engineering development, as it did with much technology, as speed and power became all-important. Chrysler worked with Continental on the development of a giant, 1,792 cubic-inch (ci) V-12 that would be used in the Patton tank. It produced 810 horsepower and 1,560 pounds-feet (lb-ft) of torque and enabled Chrysler’s engineers to gather some valuable information that they put to good use in their post-War automobiles.

In 1947, Zora Arkus-Duntov, the so-called “Father of the Corvette”, was commissioned by Ford Motor Company to improve the output of their aging flathead V8s. Zora, his brother Yuri and designer George Kudasch developed an overhead valve conversion (OHV) for the Ford V-8 that featured hemispherical combustion chambers. Tagged the “ARDUN”, which was a contraction of ARkus-DUNtov, their OHV heads looked great and increased the power, however, they were somewhat temperamental.

Only about 200 sets were made in the U.S. before Duntov moved to the U.K. to work with Sydney Allard where a few more sets were made for Allard’s J2 sports car. For many years, ARDUN heads were a much sought after hot rod accessory until the mid-90s when Don Orosco began to reproduce them. He made about 30 sets before the tooling was sold to Don Ferguson whose family continues to produce the heads albeit updated with some modern technology along with a compatible cast-aluminum block. Companies such as H&H Flatheads are known for building complete ARDUN engines.

While the Duntovs were working on the OHV Ford, Chrysler engineers John Platner, a graduate of the Chrysler Institute of Engineering, and William Drinkard, manager of the Engine Development department, got to work in 1948 downsizing that tank engine for use in an automobile.

The engine was tough and you could throw all kinds of power-enhancing devices from blowers to nitro and it thrived on it.

What they came up with was a 90-degree, 330 ci, cast-iron V8 engine with HEMI-heads. Code-named A-182, the “HEMI” was not quite ready for production and a lot of valve train development still needed to be done along with some ignition and crankshaft work.

Nevertheless, Chrysler debuted the HEMI V-8 for the 1951 model year as standard in the Imperial and New Yorker models and optional in the Saratoga. Initially, the “Fire Power” capacity was 331 ci due to an “oversquare” 3.81-inch bore and 3.63-inch stroke. With a 7:1 compression ratio (cr), it produced 180 hp and 312 lb-ft of torque but weighed a whopping 745 pounds—one head alone weighed almost 120 pounds and you’d better be wearing a belt when you lift one.

Chrysler’s DeSoto division came out with their 276-ci “Fire Dome” version in 1952 and Dodge followed suit with their 241 ci “Red Ram” in 1953. Although all three engines differed in detail, they shared the same basic architecture.

In 1955, Chrysler claimed a dual 4-barrel (bbl) Carter version the first production car to produce 300 hp. The displacement was increased in 1956 to 354 ci and the engine now produced as much as 355 hp and became the first American engine to produce 1 hp per cubic inch.

Two years later, the infamous 392 version was introduced and it was almost square having a 4-inch bore and a 3.906-inch stroke. It had a taller ‘raised deck’ compared to previous engines; however, the heads were cast with wider ports so that earlier manifolds could be used with the new heads on the new block. The following year, a single carb version with 9.25:1 cr was rated at 345 hp while a dual-carb version offered 375 hp.

The 392 is significant because it became the drag racer’s engine of choice, especially in the fuel ranks: Top Fuel, Funny Car, and Fuel Altered. The engine was tough and you could throw all kinds of power-enhancing devices from blowers to nitro and it thrived on it.

By 1958, the 392 was producing 380 hp but had reached the end of its production life. It wasn’t until 1964 that Chrysler re-introduced the engine and officially called it a HEMI. Nicknamed the “elephant engine,” because of its size and weight, the new Gen II HEMI displaced 426 ci. Not initially available to the public, it was used in NASCAR in ’64 but not in ’65 because it was not available in a production car and therefore could not be raced.

Not to be outdone, Ford also introduced a 427-ci HEMI in 1964. Nicknamed the “Cammer” because it had a single overhead cam (SOHC), engineers had worked hard to design a symmetrical combustion chamber with the plug located for maximum efficiency only to discover that the plug didn’t care where it was. The plugs were then located near the top of the cylinder for easy access. NASCAR wasn’t at all happy about these “special” racing engines, however, the “SOHC” motor (pronounced “sock”) remains a “halo” engine for Ford.

Chrysler fixed their NASCAR problem in 1966 by introducing the “street” HEMI with lower compression, a milder cam, cast instead of tube headers and two 4 bbl Carter AFB carbs. The Gen II HEMI was produced until 1971 and was rated at 425 hp at 5,000 rpm and 490 lb-ft of torque at 4,000 rpm.

Of course, this is only the American version of HEMI history. Across the pond, in the homeland of the HEMI, the Europeans never left the concept alone.

Incidentally, the 426 HEMI is a HEMI in name only. Rather than build the new 426 from the old architecture of the 392, Chrysler engineers chose to use the existing 440 Wedge-head big-block. That said, the 426 evidences many improvements over the Wedge and indeed the 392 and became the modern drag racer’s engine of choice and was known colloquially as the “late model” compared to the 392 “early model.”

As the factory HEMIs came to the end of their respective lives Ed Donovan of Donovan Engines introduced a cast-aluminum 417 ci aftermarket version in 1971 that was based on the 392. That was followed in 1974 by Keith Black’s 426 HEMI based on the factory 426. Versions up to 573 ci are now available as are heads and numerous other parts milled from billet aluminum from numerous aftermarket manufacturers such as Hot Hemi Heads.

In fact, we use a billet 417 ci Donovan block with billet heads from Hot Hemi Heads in Ron Hope’s Rat Trap AA/Fuel Altered that we race. With a billet BDS supercharger and 90-percent nitro, it produces some 3,000 hp. However, in current Top Fuel/Funny car racing they use architecturally similar 500 ci blocks milled from forged billet aluminum.

These proprietary blocks are produced in-house by Don Schumacher Racing and John Force Racing but similar blocks that can withstand in excess of 10,000 hp are available from companies such as Brad Anderson and Alan Johnson Performance—all based on that Chrysler HEMI.

Of course, this is only the American version of HEMI history. Across the pond, in the homeland of the HEMI, the Europeans never left the concept alone. For example, Daimler, using Triumph motorcycle architecture, developed two aluminum-headed HEMI engines of 2.5 and 4.5-liters.

Other British brands such as Aston Martin and Jaguar both employed hemispherical combustion chambers in the DOHC V-8s and straight 6s respectively. However, no doubt the most well-known use of their HEMI-head was by Porsche in many of their engines—particularly the flat-six boxer engines of the 1963-’99 911s.

The Jeep: From Willys to Wrangler

How the World’s Most Famous Go-Anywhere Vehicle Earned Its Stripes

If you had to pick a single candidate for “the most American car ever,” there are a lot of potential candidates. The Corvette would be near the top of the list—it’s always been “America’s sports car” from the original C1 racers at LeMans through the iconic split-window 1963 model and the C3 that defined the Apollo Era of American exceptionalism (and endured the dark days of smog restrictions and gas lines), all the way up to today’s C7 and upcoming mid-rear-engine C8 supercar.

You could also make a case for the Ford Mustang that launched the Pony Car wars and spawned the Camaro and Challenger, or the “shoebox” Chevy sedans that became a favorite of hot rodders. The original muscle car, the Pontiac GTO, would also be on the shortlist, and even the Ford Model T would be a strong contender, thanks to the way it put car ownership in the reach of the working class and created the impetus for America’s shift from roads designed for horse-drawn conveyance to ones better-suited for cars and trucks.

But out of all the possibilities, in the end there’s only one vehicle that truly deserves the title—the Jeep. In continuous production (and continually popular) since 1941 and showing no signs of ever falling out of favor, the iconic off-roader is the one motor vehicle that stands above the rest. Born in the shadow of looming global conflict, the original Jeep served admirably in the Arsenal of Democracy, transitioned to civilian life as a workhorse for farmers and ranchers, and evolved into a status symbol that never lost its off-road credibility.

While “Jeep” grew from a single, scrappy 4×4 light scout car into an entire brand that has encompassed multiple different platforms over the years, including today’s unibody SUV and crossover vehicles, what we’re really interested in is the MB, CJ, and Wrangler models that are first to mind when you hear the name “Jeep.” Here is their story.

Flat Fenders

The vehicle we know today as the Jeep began its existence as a US Army specification for a “Truck, ¼ ton, 4×4” just prior to America’s entry into the Second World War. Post-WWI, the country’s armed forces had been significantly drawn down and reorganized, and many experiments were in progress to determine how new technology would make the next conflict different from the static trench warfare that characterized the Great War.

…the original Jeep served admirably in the Arsenal of Democracy, transitioned to civilian life as a workhorse for farmers and ranchers, and evolved into a status symbol that never lost its off-road credibility.

Light trucks and cars had shown promise toward the end of that war as a way to conduct reconnaissance, quickly move troops, artillery, and supplies, and generally, replace the large numbers of horses that had previously done most of the heavy lifting. The Army had a number of vehicles already in development or production that ranged from a half-ton to 7.5 tons in payload capacity, but a need was recognized for a smaller, more agile vehicle in the quarter-ton capacity range for the reconnaissance and liaison role.

American Bantam, a manufacturer with a somewhat-troubled history of bankruptcy but plenty of experience with small cars, and Willys-Overland, another faltering Depression-era builder and seller of small cars, endeavored to produce prototypes to meet the somewhat-unrealistic specifications set out by the Ordinance Technical Committee: 4-wheel drive, a crew of three, a 75-inch wheelbase and 47 inch track width, a fold-down windshield, 660-pound payload, and an engine with a minimum of 85 pound-feet of torque, all weighing in at a scant 1,300 pounds empty. Oh, and by the way, bids were required in 11 days, with a deadline of 49 days for the first prototype and 75 days to deliver 70 test vehicles.

While Willys was the low bidder, they were passed over in favor of Bantam when they couldn’t commit to the incredibly short deadline, and the Army moved ahead with the project. Over the course of development, Willys and eventually Ford became involved, as Bantam didn’t have anything close to the production capacity that would be required for full-scale manufacturing. The specification evolved from the ridiculously-light 1,300-pound weight goal to a more sensible 2,160-pound maximum, and Bantam ended up being edged out of the project as the Willys MB and Ford GPW became the definitive production models, with the US Army securing the patent for what would be known as the WWII Jeep in 1942.

Over the course of the war, Willys would manufacture more than 360,000 MBs and Ford would build another 280,000-plus GPWs. Ford being Ford, while parts were mostly interchangeable between the two, many of the parts produced by Ford would be stamped with a stylized cursive capital letter “F” in the same font as the Ford logo.

Post-War Production

With the Second World War drawing to a close, and all of America’s manufacturing corporations eyeing the future beyond the massive expansion they’d experienced since 1941, Willys-Overland was keen to find a way to turn the MB into something that could be sold on the civilian market. In 1944 with victory in sight, they began to work on prototypes for the “Civilian Jeep,” or simply CJ, mainly consisting of removing military-specific details like blackout lights and adding a tailgate. The initial conversions would later be referred to as the CJ-1, though none have survived and details are scant. The follow-on CJ-2 prototypes would be another limited experiment with only a few scores produced for internal company testing of more civilian-friendly modifications, and a few still exist today.

These led to the CJ-2A, the first true production civilian Jeep, which introduced the now-trademarked 7-slot vertical grille (previous models had 9) and was primarily intended for the agricultural market with a wide range of factory accessories like winches, snow plows, mowers, and even welders powered off of the engine’s PTO mount. More than 200,000 were sold between the end of the war and 1949, in a bewildering array of possible configurations that have become a collector and restorer playground/nightmare.

The next model, the CJ-3A, debuted in 1949 and included more detail changes to improve the transmission, axles, and suspension, and was adopted to replace the now-elderly wartime MB and GPW Jeeps in US military service as the Willys MC, designated the “Utility Truck, M38.” 130,000 or so were produced before being replaced by the CJ-3B in 1953, with more minor changes. Kaiser (yes, the same car manufacturer that eventually spawned the healthcare company) bought Willys-Overland that same year, and licensing of the Jeep design was expanded from Mitsubishi (who had produced the 3A in post-war Japan exclusively for police and other government use) to also include Mahindra in India, who would continue to grind out CJ-3B-based vehicles all the way through 2010.

The CJ-4 moniker was applied to a stillborn concept project in 1950-51, so the next Jeep model the world would see was the CJ-5. In various versions, it would remain in production from 1955 to 1983, and it soldiered on through many changes – not the least of which came when Jeep was sold to American Motors Corporation in 1970. In military service it would be known as the M38A1, and in 1972 AMC engaged in a major revision to the platform that increased the wheelbase by 3 inches, added overall length, and increased the size of the engine bay to accommodate both a 304 cubic inch V8 and 3.8 and 4.2 liter straight six engine options.

…Jeep fans absolutely lost their minds, with the YJ being panned by hardcore enthusiasts as an unworthy successor to the legendary CJ series.

AMC’s marketing increasingly targeted mainstream buyers instead of the agricultural and utilitarian appeal previous Jeeps had cultivated. Multiple appearance, accessory, and performance packages were offered, leaning heavily toward the stickers-and-stripes design ethos of the 1970s and early ‘80s.

A stretched-wheelbase version of the CJ-5 was designated as the CJ-6 and was produced between 1955 and 1981, but most of the 50,000 or so units made ended up overseas, with US availability ending in 1975. As a hint of things to come, a 4-door version was available, but never caught on domestically. The definitive “Civilian Jeep” model, the CJ-7, debuted in the 1976 model year in the US in production that overlapped its predecessor. It was visually distinctive from the CJ-5 primarily due to different door cutouts, but also featured changes to the ladder frame beneath the bodywork that allowed wider placement of the rear leaf springs for more chassis stability—the CJ-5 had been somewhat unfairly faulted for being dangerous in sudden obstacle avoidance maneuvers, and the suspension improvements were intended, in part, to address that issue. As the last of the classic Jeep models that could draw their lineage directly to the original WWII MB and GPW, almost 380,000 were built before the sun set on the CJ series in 1986.

Meet the Wrangler

For 1986, AMC (now owned by French auto conglomerate Renault) introduced a mostly-clean-sheet replacement for the CJ-7 named the Wrangler, with the internal chassis code YJ. The redesign continued the trend toward more safety and comfort features, but retained the Jeep essentials—leaf-sprung live axles front and rear, body-on-frame construction, a folding windshield and removable doors, and a strong bias toward off-road competence over everyday practicality. Nevertheless, Jeep fans absolutely lost their minds, with the YJ being panned by hardcore enthusiasts as an unworthy successor to the legendary CJ series. The distinctive square-headlight Wrangler continued in production through the purchase of the Jeep brand by Chrysler in 1987, with total production topping 685,000 units before the final 1995 production year.

Remaining 1995 YJ production models continued to be sold through the “missing” 1996 Wrangler model year, and the new TJ made its debut for 1997. Bowing to the power of nostalgia, the new Wrangler went back to round headlights, but introduced a major change to the suspension in the form of coil springs in place of the front and rear leaf spring setup that dated back to 1940. Once again, Jeep purists were enraged, but the Wrangler gained another major improvement in everyday on-road practicality in exchange for essentially no loss of off-road competence. The top engine option remained as a modernized 4.0L version of the venerable AMC straight-6, with 4-cylinder power in base models. A “Wrangler Unlimited” model, still retaining the 2-door body configuration but stretched 10 inches in wheelbase and 15 inches overall compared to the standard TJ, debuted for 2004, offering better room in the back seat and greatly improved towing capability.

TJ production wrapped up in 2006, and Jeep introduced the JK Wrangler for the 2007 model year. While still retaining live axle suspension and styling that was very similar to the TJ, the JK was a complete redesign that was wider and longer in wheelbase (though shorter overall) than its predecessor. Most importantly, the Wrangler Unlimited, AKA the JKU, introduced a true 4-door option with a 20-inch longer wheelbase while being less than 3 inches longer overall than the previous TJ Unlimited. This decision turned out to be hugely successful, with the overwhelming majority of JK buyers opting for the 4-door Unlimited model. Finally giving in to the inexorable march of progress, hardcore Jeep fans have embraced the JK/JKU, and the aftermarket has shown incredible enthusiasm for the third-gen Wrangler with an enormous variety of suspension, engine, and body upgrades.

For the 2018 model year, Jeep introduced the JL, which continues the tradition of body-on-frame construction and live front and rear axles, with more concessions to the luxury and comfort features buyers of the increasingly-expensive Wrangler have come to expect. While it remains the most competent off-road domestic vehicle you can buy off the showroom floor, especially in “Rubicon” trim, today’s Wrangler has come a very, very long way from the tiny “go-devil” known to US troops in WWII. Over the past eight decades, Jeeps have gone from a thrown-together way to haul a few soldiers and their gear across inhospitable terrain to luxury mall-crawler and every point in between. In the process, they’ve become the most uniquely American form of transportation, recreation, and personal expression, and there’s no end in sight.