The 2021 Ford Bronco: What to Expect

The Blue Oval Boys Take On the Jeep Wrangler on Its Home Turf.
Do They Have the Right Formula to Unseat the King of Hardcore Off-Roading?

For the last 75 years, Jeep has been the brand to beat when it comes to street cred where the streets end. From the original civilian CJ-2A to today’s JL Wrangler, they’ve set the standard for no-compromises off-road performance straight off the showroom floor. Throughout that long, successful run they’ve faced many challengers; the Toyota Land Cruiser, the Chevy Blazer, the International Scout, and of course the Ford Bronco.

Though they all found their own fans, over the past few decades all those nameplates have fallen to the wayside, leaving only Jeep still selling vehicles that are so strongly biased in favor of all terrain performance over creature comforts and day to day practicality.

Now, Ford is poised to take a run at the Wrangler with the 2021 Bronco, which will be revealed in full to the world on Monday, June 13, 2020. This long-rumored return of a classic off-roader shows every sign of being specifically targeted at the same market segment as the JL, but can it really go toe-to-toe with Jeep’s flagship? Here’s what we know so far…

There Will Be Three Different Broncos

This is a mortal lock, based on what Ford has already shown us. The lineup will include a 2-door, a 4-door, and the Bronco Sport. But honestly, you can just ignore the Sport – it isn’t going to share anything but a nameplate with the “real” Bronco, and is going to be positioned as a competitor to softroaders like the Jeep Renegade, not the Wrangler. A pickup version to compete with the Jeep Gladiator is possible as a follow-on in subsequent model years, depending on how sales of that model (as well as the 2- and 4-door Bronco) pan out.

The Doors Will Be Removable (Without Tools)

US Patent 10,550,615 B2 granted to Ford in February describes a “door hinge assembly incorporating a latch to facilitate selective door removal.” Unlike the Wrangler, it seems that the Bronco’s doors will be easy to remove and replace without needing any tools. Ford has also filed multiple patents for things like doors with separate skins that leave a side-impact protection structure in place when removed, an airbag compatible with a detachable door, and even retractable safety rails between the front and rear pillars that are either constantly in place when the doors are off, or activate automatically in the event of a crash. Ford would undoubtedly prefer for you to keep the doors on your new Bronco while driving on the road in the name of greater occupant safety (and will also certainly put a lot of warnings about it in the manual, where nobody will read them), but based on the fact that the hinge latch patent has not just been applied for but granted, that seems very likely to be incorporated at launch.

The Bronco Will Have Body-On-Frame Construction and a Solid Rear Axle With IFS

The rumor is that the Bronco will be built on the same platform as the new mid-size Ranger pickup in the same facility, and that implies a separate traditional ladder frame instead of unibody construction. That’s good news for the aftermarket, as it will allow body lifts to easily accommodate larger-diameter tire fitments without re-engineering suspension components, plus many people will prefer that design’s inherent ruggedness for serious off-roading. The Bronco will also almost certainly have a coil-sprung solid rear axle with a multi-link suspension, but unlike the Wrangler, the front suspension is going to be independent. This is a wise move for Ford; IFS is the right answer for 95% of the questions asked of the Bronco both on and off road, and they don’t have to worry about a small but extremely vocal cadre of purists raising a ruckus like Jeep will when they inevitably have to switch the Wrangler over from a solid front axle. 

There Won’t Be a Traditional Transfer Case and 4-LO

This prediction is more speculative than some of the others, but images circulating on the interwebs point to a manual gearbox with a ratio labeled “C” on the shifter rather than a separate lever/button to engage low range. Ford has plenty of experience with 4WD systems, from full time to shift on the fly to manually-selectable, but this is a new twist. In addition to a ‘creeper gear’ you can also expect selectable locking for the front and center differentials, and either a limited slip or locker for the front as well. 

Want a V8? That May Be a Long Wait for a Train That Doesn’t Come

Way back in the early 1990s, Ford decided that the future of their powertrains lay in the direction of smaller-displacement engines with more sophisticated designs to replace their tried-and-true pushrod V8 design. While there’s much to be said about whether overhead cam V8 engines were the right idea for their trucks as well as their passenger cars, they have remained steadfastly devoted to the idea of high technology instead of raw cubic inches.

On the dyno, either engine choice for the new Bronco absolutely murders the old SBF V8…

For the Bronco, it’s very likely that the workhorse “base” engine will be the 2.3 liter EcoBoost 4-cylinder delivering something in the neighborhood of 270-280 horsepower and 310 pound-feet, biased toward low-end horsepower and torque. The optional upgrade is likely to follow the rest of Ford’s truck lineup with the twin-turbo 3.5 liter EcoBoost V6, producing around 375 horsepower and 470 pound-feet. 

On the dyno, either engine choice for the new Bronco absolutely murders the old SBF V8, but buyer acceptance is going to come down to whether the market they’re trying to court (both in terms of people with fond memories of Broncos past, and would-be Jeep Wrangler owners cross-shopping) believe that a turbocharged small-displacement engine is the right solution. Engine calibration is going to make or break the success for the new Bronco among shoppers who are looking for off road competence, and the benchmark Wrangler JL offers not only a standard naturally-aspirated 3.6 liter V6 gasoline engine rated at 285/260, but an optional 2.0 liter turbo inline four with 270 horsepower and 295 pound feet, plus a turbocharged 3.0 liter EcoDiesel that delivers an estimated 260 horsepower and 442 pound-feet.

Offering a 5.0 liter gasoline V8 based off the current Coyote architecture would seem to be an attractive option for Ford, should customers desire a NA engine over the EcoBoost 4 and 6 cylinder powerplants, but considering how the wind has been blowing with their Raptor models, a hopped-up EcoBoost V6 seems more likely as a future ‘premium’ engine upgrade.

It’s Ford’s chance to show the world what they can do when they’re turned loose to compete with the current heavyweight champ.

The Devil in the Details

While we feel we are on pretty solid ground with these predictions, Ford has kept most of the details for the new Bronco very close to the vest. You can be sure that every engineering, styling, and marketing decision for the new model was vetted against the Wrangler archetype, though – the company has a clear vision of what they’re trying to accomplish with 2021 Bronco, which is something pretty rare these days when focus groups, shareholder opinions, and low-risk strategies dominate new car and truck designs. That’s what’s really exciting about the upcoming reveal. It’s Ford’s chance to show the world what they can do when they’re turned loose to compete with the current heavyweight champ.

The Rotary Revolution

In the 140-plus years since the modern internal combustion engine was invented, there have been a countless variety of different designs; 2-, 4-, and even 6-stroke cycles, inline, vee, W, X, H, and horizontally opposed cylinder arrangements, combustion chamber shapes ranging from flathead to hemispherical, and all manner of the different valve and camshaft configurations. The technological pressure cooker of wartime development brought forth oddities like the Great War’s rotary piston engines that spun the entire crankcase and cylinders around a crank firmly bolted to an aircraft’s nose. Those evolved into radial engines with stationary crankcases, culminating in massive 28-cylinder beasts displacing more than 4,000 cubic inches and delivering 4,300 horsepower by the end of the Second World War. Then, there was the truly strange “Deltic” design that arranged three crankshafts at the corners of a triangle, each powered by pistons that moved in opposition to each other, with no cylinder head at all.

It’s the sort of mechanism that feels like it was reverse-engineered from a crashed UFO, or taken straight from the Old Testament book of Ezekiel compared to a piston engine.

But whatever form even the strangest of those engines took, they all shared one design feature that Nikolaus Otto, the creator of the first modern internal combustion engine, would instantly recognize: A reciprocating piston moving back and forth in a cylinder bore, translating linear motion into rotation via a connecting rod and crankshaft. It’s a concept so simple and elegant, but so well-suited to the task that the overwhelming majority of internal combustion engines have employed it. Though they’ve grown in sophistication over the years with new materials and manufacturing techniques, decent piston engines can be made using very basic design skills and fairly simple machine tools. Because of how difficult it is to build a “better mousetrap” than a piston engine, almost every attempt has fallen short in one way or the other and been forgotten, with one notable exception: The Wankel rotary.

Thinking Outside the Box (Or Tube, in This Case)

First conceived in the late 1920s by German engineer Felix Wankel, despite having only two main moving parts, the rotary engine’s principle of operation isn’t intuitive at first glance like a conventional piston engine. The Wankel goes through the same four stages as a piston engine – intake, compression, combustion, and exhaust – using a bowed triangular rotor that moves around an oval housing (technically, an ‘epitrochoid’ shape, a word that means “you didn’t do well enough in your Trig class to understand what’s going on here”) on an eccentric shaft. A fixed gear on the side of the housing engages a ring gear on the inside of the rotor so that for every complete turn of the rotor, the eccentric shaft turns three times.

It’s the sort of mechanism that feels like it was reverse-engineered from a crashed UFO, or taken straight from the Old Testament book of Ezekiel compared to a piston engine. But the important thing is that the motion of the rotor within the housing causes the volume between the rotor face and housing to vary in a useful way, just like the rise and fall of a piston in a cylinder bore. Though Wankel filed his first patent for the rotary engine in 1929, it would take until 1957 for him to develop a working prototype while employed at the German NSU car company. His original prototype, while using the same general principle as the rotary engines we are familiar with today, was somewhat more complex with a rotor housing that spun inside an outer casing as well as the moving rotor on the interior.

Working in parallel (and without Wankel’s knowledge), NSU engineer Hanns Dieter Paschke also developed a working prototype stationary-housing rotary engine in 1957, and it would be this design that evolved into a practical car engine. Intrigued by the potential of the Wankel, auto manufacturers from around the world, including AMC, Ford, General Motors, Citroën, Mercedes-Benz, and even Rolls-Royce licensed the design to develop their versions, but in the end, Mazda was the only company to produce Wankel rotaries in any significant quantity. While the rotary had some significant advantages over conventional piston engines, it also had several drawbacks that were inherent to the design, plus several non-trivial technical hurdles to overcome before it was suitable for mass production.

You Win Some, You Lose Some

On the positive side, the Wankel ran with a smoothness that no piston engine could match. In television ads, Mazda used a catchy folk song with the chorus, “Piston engine goes (boing, boing, boing), Mazda engine goes ‘hmm’” to emphasize that attribute. The lack of reciprocating parts also meant that Wankels could safely turn RPM numbers that would float the valves on any conventional production line piston engine, limited only by the strength of the rotor and stationary gears and what the engine-driven accessories like the alternator and water pump could endure.

In terms of size and weight, rotaries are extremely compact and light for their power output. Though they commonly had their displacement described in terms of a single chamber on each rotor’s volume (making the ubiquitous Mazda 12A and 13B rotaries nominally 1.2 or 1.3 liters), the fact that there were three such chambers for each rotor made them perform more like an engine with twice the stated displacement.

…NSU’S struggle to build production rotaries that didn’t blow bits of apex seal out the exhaust was the major reason the Wankel quickly gained a reputation as an unreliable engine.

As far as drawbacks go, the first problem facing anyone trying to make the Wankel practical as a production car engine was creating effective and durable seals. In a conventional piston engine, the gap between the piston and the cylinder wall is sealed by a ring package that uses a combination of gas pressure directed into the ring lands and the pressure differential between the area above and below the ring itself to dynamically load the top ring and keep it at the proper tension. While modern piston ring design and the materials used have become very complicated and sophisticated, simple iron rings with a square profile will do the job quite nicely if you’re not trying to squeeze out that last few percentage points of power and efficiency. As a bonus, circular rings are a piece of cake to manufacture to precise tolerances as well.

This isn’t the case with a Wankel. A look at how the rotor oscillates in the housing tells you that you’re going to need three long, gently curved seals on either side of the rotor, plus three seals at the apex of each point of the rotor’s triangle to separate the individual “combustion chambers” from one another. While the side seals didn’t turn out to be a big deal, coming up with apex seals that were durable enough for a production car ended up being a real challenge. NSU’s struggle to build production rotaries that didn’t blow bits of apex seal out the exhaust was the major reason the Wankel quickly gained a reputation as an unreliable engine.

Mazda managed to develop reliable apex seals for their rotaries, but another challenge came from the fact that unlike a piston engine, where the cylinder bores are continuously lubricated by oil slung from the connecting rod bearings as the crankshaft spins, there’s no convenient way to get lubrication to the apex seals. The solution came from injecting small amounts of engine oil into the intake airstream, providing the same end result as premixed fuel and oil for a 2-stroke dirt bike or chainsaw.

In the end, rotaries proved to be more trouble than they were worth, even for Mazda, at least in terms of production car use.

Unfortunately, about the same time Mazda got that issue figured out, the oil crisis of 1973 sent fuel prices skyrocketing, and in the US, emissions standards began to be taken seriously. This double whammy hit the Wankel where it lived – although the engines were efficient in terms of size and weight for their power output, their Brake Specific Fuel Consumption (the amount of gas required to produce a particular amount of horsepower) was poor compared to a conventional piston engine and having to constantly inject a bit of oil mist into the engine inevitably lead to unavoidable higher hydrocarbon emissions.

Thermodynamics Is a Harsh Mistress

As it turns out, a piston engine with cylindrical bores is about the best practical shape for keeping heat contained inside the combustion chamber, since it has the least surface area for any given volume. The arcane geometric wizardry that makes a Wankel even possible also dictates that the constantly changing combustion chamber shape is going to have a lot of surface area for the engine’s displacement, which means that a disproportionate amount of the heat energy from burning fuel is going to end up slipping away into the rotors, side housings, or endplates instead of doing useful work. That unavoidable fact meant that rotaries would never be able to match a conventional piston engine’s fuel economy pony for a pony, even when installed in a car optimized for the Wankel’s lightweight.

There are other quirks to rotary engine design as well – because of that oddly-shaped combustion chamber, Mazda used two spark plugs per rotor with staggered ignition timing to make sure the air/fuel charge burned as completely as possible. Additionally, variable cam timing and/or valve lift can dynamically change the characteristics of a piston engine’s combustion cycle, but a Wankel engine’s intake and exhaust timing are fixed, much like a valveless two-stroke engine, dictated by the position of the ports on the side housings and periphery of the center housing.

The Wankel Legacy

In the end, rotaries proved to be more trouble than they were worth, even for Mazda, at least in terms of production car use. The end of the line for the venerable original 13B, which remained in production for an astonishing three decades, came with the end of FD RX-7 production after the 2002 model year. By then, the 13B-REW had evolved into a twin-turbo 280 horsepower plumber’s nightmare of vacuum lines and emissions control hardware that was far removed from the simplicity promised by the original Wankel design. Its successor, the naturally-aspirated 13B-REW RENESIS found in the 2003-2013 RX-8, improved emissions, and fuel economy via a radical rework of the exhaust port location and truly heroic engine control calibration efforts, but ended up falling short of ever-more-restrictive emission limits in the US and Europe nonetheless.

…the real legacy of Herr Wankel’s inspired engine design is the unmistakable sound of a three-rotor peripheral port engine banging against the rev limiter at the race track, sounding like a cross between a machine gun and the end of the world.

Mazda continues to experiment with Wankel engine design, showcasing things like hydrogen-fueled rotaries that burn much cleaner than gasoline-powered designs in concept vehicles, but it’s unlikely that we’ll ever see the widespread enthusiasm for this radically different kind of internal combustion engine as we did in the late 1960s and early 1970s again. For niche applications where a high power-to-weight ratio and compact dimensions are critical, the rotary will retain its popularity, but the real legacy of Herr Wankel’s inspired engine design is the unmistakable sound of a three-rotor peripheral port engine banging against the rev limiter at the race track, sounding like a cross between a machine gun and the end of the world.

Spray to Play

Nitrous and the N2O Need-to-Know

Call it spray, squeeze, juice, the bottle, or simply “naws” – nitrous oxide is one of the high performance world’s most popular power-adders, as well as being the most misunderstood. Because it’s easy to conceal a nitrous oxide injection setup, many consider it to be ‘cheating.’ Because it’s easy to give an engine more than it can safely handle, many consider it dangerous to your car’s health. Today, we’re going to take a quick look at how it works, bust a few myths, and tell you what you need to know about N₂O.

Nitrous oxide is a chemical compound consisting of two nitrogen atoms bound to a single oxygen atom. First synthesized in 1772 by Joseph Priestly (who was the guy who arguably was the first chemist to discover and isolate oxygen), by the mid-1800s its effects on human consciousness had led to its use as both an anesthetic for medical purposes and a party drug, both of which continue to this day.

It took another century for its usefulness as a power-adder for piston engines to be widely recognized; during the Second World War, many Luftwaffe fighter aircraft were fitted with what was referred to as the GM-1 system of nitrous oxide injection that greatly improved engine performance at very high altitude. Post-war hot rodders in the US made sporadic use of the gas, but in the late 1970s, the aptly-named Nitrous Oxide Systems (or NOS) company popularized it by producing the first widely-available kits and components that made it relatively easy to use without an engineering degree.

How Nitrous Works

People will often say that an engine is “like an air pump” – while that analogy is useful to a point, a better analogy would be a forge. Pump more air into the forge with bellows, and the fire gets hotter and more intense. The energy an engine can produce is directly related to how much fuel it can efficiently burn, and in order to create more horsepower, you have to burn more fuel, more quickly. In a high-performance naturally-aspirated engine, multi-valve cylinder heads and high RPM do the job of rapidly combining fuel and air into a mixture that can be ignited and turned into pressure to move the pistons. In a turbocharged or supercharged engine, a mechanical compressor forces additional air into the cylinders for every combustion cycle, and the additional air allows more fuel to be burned and converted into useful work.

In an engine with nitrous oxide injection, instead of increasing the rate of combustion events per second, or forcing more outside air into each one of those events, the composition of the intake air gets changed. The normal air we breathe is about 21 percent oxygen, give or take, while nitrous oxide brings one oxygen atom to the party for every two nitrogen atoms – about a 12 percent increase in the oxidizer available to burn more fuel.

“Why not just use pure oxygen instead?” you might ask. The answer is that nitrous oxide has another trick up its sleeve. Because it takes energy in the form of heat to decompose it into nitrogen and oxygen molecules, using N₂O as an oxidizer has a ‘buffering’ effect. At around 1,050 degrees F inside the combustion chamber, the oxygen is liberated, but not before absorbing some of the heat of combustion to power the reaction, slowing and controlling it. Pure oxygen fed into an engine will cause something more like an explosion than a controlled flame, but nitrous oxide is well-suited to the task of burning more fuel, without an uncontrolled reaction.

Nitrous oxide also has the benefit of cooling the ‘normal’ intake air charge as well. Stored as a liquid under pressure, when it’s released into the intake tract it flashes to a gaseous state, and the energy required for this phase change super-cools the air around it. This increases the density of the intake charge, delivering more air to mix with the available fuel and further adding potential power.

Nitrous System Terminology and Technology

There are two basic kinds of nitrous oxide systems: “dry” and “wet”. Dry systems only add nitrous oxide to the intake charge, while wet systems provide both N₂O and additional fuel. Dry systems were developed first, and relied on carburetors or mechanical fuel injection calibrated to run very rich when the system wasn’t in operation, so they wouldn’t be dangerously lean when the nitrous began to flow. Modern dry systems are a different story – they’re typically connected to an electronic fuel injection system that can provide the desired amount of additional fuel on command upon activation.

Wet systems are designed in a way so that when the system is activated, a calibrated dose of both fuel and nitrous oxide is delivered to the intake airflow at the same time. Both types of systems can introduce nitrous or the nitrous/fuel mix at a single point in the intake plenum, through a plate with spray bars or slots, or via individual nozzles located in each cylinder’s intake runner.

Nitrous oxide is stored in a self-pressurizing tank, with a capacity measured by the weight of its contents – ten and fifteen pound tanks are the most common. The tank is partially filled with nitrous oxide that is in a liquid state, topped by nitrous oxide gas. A siphon tube extends down to the bottom of the tank and leads to a valve that supplies the system. The pressure in the tank is determined by its temperature, and as nitrous flows out, some of the remaining liquid “boils off” inside the tank. To maintain temperature, a thermostatically-controlled electric heater can be used; sometimes you will see racers use a propane torch to heat a bottle, but this is an extremely dangerous practice as it can lead to weak spots in the tank that may not cause it to blow up on the spot, but that can lead to it catastrophically failing in the future when it is being refilled.

Nitrous flows from the valve up to the engine bay, where a solenoid (an electrically-operated on/off valve) controls the activation of the system. Wet nitrous setups will have a solenoid to control the flow of additional fuel as well, which is activated by the same circuit as the nitrous solenoid. One popular addition to the nitrous plumbing is a “purge solenoid” located adjacent to the main nitrous solenoid – by momentarily opening it, gaseous nitrous oxide is purged from the supply line and liquid is brought all the way up to the main solenoid, so that when the system is first activated it won’t briefly run rich.

Past the solenoids, the nitrous (and fuel in a wet system) proceeds to the plate or nozzle where it will be injected into the engine. At the connection to the plate or nozzle, a ‘jet’ is inserted inline to regulate the flow. Jets are made from brass, stainless steel, or other similarly durable materials and have small, very precise holes drilled through them. These orifices, measured in thousandths of an inch in diameter, are used to calibrate the oxidizer and fuel mixture. System manufacturers provide charts that explain, “With this nitrous jet, and this fuel jet, your engine will produce this much extra horsepower.”

It’s worth noting that the horsepower provided by a particular jet combination is constant, whether the engine is a 1.6 liter 4-cylinder or a 500 cubic inch big block V8, and it’s not dependent on engine RPM either. “100-shot” jetting is going to be very, very hard on a small four-banger, but is usually going to be OK with a large displacement eight cylinder engine. Even the V8 is going to have a hard time digesting that much fuel and nitrous below 2,000 RPM, though, because there aren’t going to be very many combustion cycles per second to safely burn all that extra fuel.

To increase the safety of a nitrous system, it’s possible (and advisable) to include components like a ‘window switch’ that will prevent the system from operating below or above preset RPM limits, a fuel pressure switch that shuts things down before the engine runs too lean, and even sophisticated progressive and multi-stage controllers that can pulse the solenoids many times per second instead of leaving them wide open as well as actively reducing ignition timing to prevent detonation. This allows the user to create a customized power delivery curve for the nitrous assist instead of it being a simple on/off proposition. But all of that aside, the most important advice to a would-be nitrous oxide user is “don’t be greedy – follow the manufacturer’s recommendations.”

Because it’s so easy to switch jets in a nitrous system (sometimes known as ‘pill it till you kill it’), the temptation is always to step things up and see what happens. But when used as directed, nitrous oxide is a safe, inexpensive, and effective way to significantly increase the performance of almost any engine.

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.