Photos by Fastest Street Car, Courtesy of the Manufacturers
If you have ever wanted to stump one of your hardcore racing geek friends with a factoid, start with making them tell you the first displacement and application of the Chrysler Hemi engine. They will likely talk to you about the 331ci FirePower Hemi that debuted in 1950, and was first used in 1951 model year cars. That engine was rapidly adopted by hot rodders and before long, it got a reputation as a tough customer on the street and strip. They’d likely tell you all of that and they would be not only a little wrong, but as you will learn in a couple of minutes, they would be colossally wrong.
The Chrysler Hemi is undoubtedly one of the best engines that a Detroit manufacturer has ever dreamed up and produced, but is it the greatest drag racing engine ever? We’re going to examine the history of the engine, the construction of the engine, and the factors that play into it being favored in so many applications. We’re also going to talk to the experts who build the parts that drag racers use, and the talented mechanics that build the engines powering some of the sport’s craziest stuff. Is the Chrysler Hemi the greatest drag racing engine ever? Let’s try to figure it out, one way or the other!
The First Hemi
So your buddy the “expert” has given you the full story on the early 331ci FirePower Hemi, and he’s confident that he’s crushed your lame attempt at stumping him, except he hasn’t. While that engine may have been the one to debut in cars, the first Chrysler Hemi was born for the skies. Displacing 2,220 cubic inches, measuring 10ft long, and making 2,500hp with the help of a turbocharger and a centrifugal blower, the original Hemi debuted in 1945 as an engine for warplanes. Unfortunately for Chrysler, the war was all but over when running examples of the engine, called the XIV-2220, were actually produced. Intended for the P-47 Lightning, a few test engines took to the skies, but the engine line was never used in active combat situations.
The engine was a bad Jose, producing 1.03hp per lb, which was a fantastic number for the era, and it was capable of making full power all the way up to 25,000 ft, which was another big deal. When the point of the engine is to run down and shoot the bad guys out of the sky, you need as bad a flying hot rod at 25,000 ft as you did at 10 ft. The engine may not have made it into a full production run, but its development educated Chrysler engineers on many of the design elements that they would continue to tweak on and refine into following generations of the engine.
Like so many mechanical innovations that would go on to have a big impact on the world, the roots of the Chrysler Hemi are forever attached to the max effort that the United States put forth to win WWII.
The Whats and Whys Of A Hemi
Chrysler’s modern marketing efforts have brought the word Hemi to the tips of many people’s tongues that have no idea what it means. They know it stands for horsepower and it is something that they want in their car, but outside of that, many likely believe that the term itself is some kind of catchy made up word. It is not.
Hemi is short for “hemispherical”, which references the shape of the cylinder head combustion chamber in one of these vaunted engines. Unlike “normal” engines that use a wedge shaped combustion area to squash and ignite their fuel, the Hemi has one shaped like a sawed-in-half grapefruit. Much of the magic lies in this design for a few basic reasons.
The first is heat loss. A Hemi head holds onto its heat better in the combustion chamber, which means hotter and more complete combustion of the mixture when it is fired. The second is the fact that the hemispherical chamber allows for very large valves to be used, and those valves are arranged in a cross-flow layout rather than in line with each other, further helping efficiency. Inline-valve engines typically run into problems with valve-to-cylinder-bore clearance and that in turn limits things like port design, which hampers ultimate power. A full race-designed Hemi head is a thing of brutal simplicity. The ports are like straight-shot tunnels to the backside of huge valves, which is one of the reasons why modern race Hemi engines produce such prodigious power in both naturally aspirated and boosted forms. There are downsides, though.
The biggest weakness these engines suffer from is valvetrain geometry. With a single camshaft in the block and valves that are opposed to each other in the head, getting the movement of the pushrods to actuate said valves requires parts and pieces that are very large, very long, and comparative to other engines, very heavy. Companies like Brad Anderson Engineering, Alan Johnson Performance Engineering, Jesel, and others manufacture very hardcore components to survive the environments that racing provides, but even these great names have their limitations. Over the years the parts have swelled in size. For instance, pushrods out of a top shelf Pro Mod Hemi engine could be used to beat someone into submission. They are bat-like. The rockers are supersized as well, and refined versions of the original stuff that Chrysler was producing 50 years ago.
The Race Hemi Family Tree
This story is based around the second-generation Chrysler Hemi, which was produced from 1964 through 1971 and is the favored design for racers in Pro Modified and various small-tire drag racing categories as well. It should be mentioned that the first-generation engines had a huge impact on drag racing, and interestingly, the first aftermarket racing block produced specifically for drag racing, the Donovan 417 was Ed Donovan’s take on the ultimate Gen-1-style engine.
Why did he build it? By the time 1971 had rolled around, the iron blocks were getting scarce and racers were killing them at such a fantastic rate that there was definitely a market for a lighter and stronger solution to then decade-old, cast-iron units. Based off the architecture of the 392-style engine, the Donovan 417 was immediately successful and widely used in the nitro ranks. Amazingly, an updated variant that follows the same design is still used in many nostalgia nitro-burning cars today. The aluminum block filled with steel cylinder liners stopped the rampant cylinder wall failures that were killing the factory blocks racers were relying on.
But you are asking yourself, “If the 426 race Hemi came out in 1964, why were people still stuck on the older 392 design?” Simply put, racers had no idea what they were missing. Guys like Don Garlits, who were sponsored by Dodge, got on the 426 train early, but the results were less than spectacular. Why? They had not yet figured out that by running the same tune up in a 426 engine as they were in a 392, that they were leaving big power on the table. The 392 engines would split the cylinder walls with little more than 30-degrees of timing lead in them. The 426 engines were more robustly built and as soon as racers figured out that up to 50-degrees of lead wouldn’t kill them, it was on. Garlits tells a famous story about finding 20 mph over the course of a weekend while literally attempting to blow up an engine he was frustrated with. The more lead he gave it, the faster the car went.
In 1973, Milodon produced the first aftermarket 426 race block and they were followed by the likes of the legendary Keith Black, Joe Pisano, and in today’s world, operations like Brad Anderson Engineering, Noonan Race Engineering, CN, and others. These race blocks raised the game immediately for the same reasons that the Donovan did for the 392. Correcting the weaknesses that racers exploit allows tuneups to get more aggressive and the power levels to continue to rise.
The Modern State of Hemi Affairs From The Experts
On any given NMCA race weekend, one is liable to see more Hemi engines in action on the drag strip than the normal cruise-night goers sees in a year of hamburger-stand visits. Categories like Nostalgia Muscle Car have loads of 426ci or 426-variant engines in them. These are typically naturally aspirated engines running on racing gasoline or alcohol with carburetors on top. The suppliers for cylinder heads and associated components are seemingly endless for these engines. As we move up the performance ladder into the heads up categories, we continue to see the Hemi presence but it becomes more specialized.
The Engine Builder’s Opinion
Ray Barton is one of the most well known names when it comes to builders of Chrysler Hemi engines. The man has built more than 150 killer Super Stock versions of the engine along with countless others for both street and strip use. His opinions on the Hemi? They’re strong. When asked if he thought the Hemi was the best drag racing engine ever his response was swift, “What else is there?”
“Back in 1984, we had just cracked 700hp and set the national record,” Barton said. “I knew in my heart that these engines could make more and more power, but the guys at Chrysler were begging me to give up on them because they were dinosaurs!” Barton continued, “They wanted me to race some of the B-1 wedge stuff or turbocharged four cylinders, but we stuck with what we were doing.” When asked about where his greatest development and improvements have come over the years, cylinder head work and valvetrain evolution were his answers. “Just recently we had some of our newest stuff on the Spintron here at the shop and we held it at 10,000 rpm for 10-15 seconds to see what would happen,” Barton explained. “It all survived, which is great and what we wanted to have happen. Not too many years ago when we were spinning the engines to 7,000 rpm, valve springs would fail on every pass like clockwork.”
If Ray Barton had been in the room when Tom Hoover and the engineers were putting the finishing touches on the Hemi design more than 50 years ago, would he have changed anything before the ink dried? An eight counterweigh crankshaft and some more work on the valvetrain knowing then what he knows now, we’re guessing!
The Block and Head Manufacturer’s Take
Noonan Race Engineering has been grabbing headlines for the last several seasons in some of the highest powered, boosted, drag racing Hemi applications across the globe so we gave them a call to talk about the Hemi’s greatness and evolution. Darrell Makins was the guy we peppered with questions regarding the iconic engine and his answers were telling.
“The real evolution in the Hemi engine these days for us is moving from the traditional 4.8-inch bore spacing to a 4.9-inch bore space block,” Makins said. “This allows us to unshroud the valves and it allows for larger-bore combos than we have had before. Instead of a 4.500 bore, we can go 4.600 and instead of 2.450 intake valve, we can now go as big as 2.600. All of this adds up to more power.”
Interestingly, Makins said that Noonan has been applying things that they are learning from Pro Stock engines and the company’s LS engine program as well. “One of the things that’s interesting is in regard to camshafts,” Makins said. “A standard Hemi cam is 48mm. We’re getting near Pro Stock sized 70-75mm cams in these engines now with lifters that are over an inch. Valvetrain is really where things are growing by leaps and bounds. More rpm means more power, especially when we are talking about overdrive-limited blower applications.”
Noonan has also created a billet, water-jacket block designed for use in some of today’s fastest growing segments of the sport.
“The water jacket block is designed for racers who are looking to push the limits at events like Drag Week, or those who compete in No Prep events, do Street Outlaws style stuff, etc.”
At the end of the day, Makins said that most of the changes being made in today’s drag-racing world with the Hemi are about strength.
“Everyone is working to make a better part,” Makins said. “We have better materials and fasteners to secure things. We used to torque heads to 100 ft/lbs and now we’re going to 180 ft/lbs. We’re using 6061 alloy that’s super strong and can maintain the integrity of things like the crank alignment better, etc.”
Makins final take on the Hemi? “I think if you got one of the engineers from the 1950s or 1960s and showed him our modern engines, he’d recognize it as his basic design. It is still a crossflow engine, the motor mounts are still the same and they bolt in the same place. Things like combustion chamber design have changed radically over the years, but it is pretty neat that the basic foundation of what was created is still there and we’re all working to make it even better and stronger.”
The Tuner’s Perspective
To get a tuner’s perspective on the Hemi’s role in drag racing we caught up with Scott Clark, a guy who has experience working with these engines in a bunch of roles, all the way up to the hairy chested turbocharged versions found in many Pro Mods. “One of the biggest things the Hemi has going for it is development,” he said. “The package and the parts that these engines are comprised of have been raced and refined to an amazingly high level. When I think back to the original design of the second-generation engine and what it laid the ground work for, I have to believe that the fact Chrysler engineers could focus on performance and not be restrained by emissions or packaging concerns set the foundation for what we have today.”
In terms of tuning, Clark has some interesting observations.
“The hemispherical chamber may not be the greatest for efficiency, but you can cram a lot of air into it and the layout lends itself to a near-optimal head design with no very tricky turns to get the air into the chamber,” Scott said. “Typically when I am asked to work with a hemi-style engine, I don’t expect to run into some of the cylinder distribution issues that are present in some other engine types and designs.”
Because boost has become the lifeblood of drag racing, we were wondering why the Hemi seems to really shine when force fed and Clark again had interesting insight.
“The Hemi really shines in places where boost is limited. Take a Pro Mod class that regulates turbo cars on a specific boost number. Boost is a measure of restriction, nothing else, that means the more efficient the engine is the more air you’ll be able to move at a given boost pressure, right?” In classes where boost is not restricted the potential advantage that the Hemi has goes away a little, and wedge-style engines are more apt to be competitive according to Scott.
The bottom line is that Chrysler engineers 50 years ago created a basic platform that racers have improved and altered over the years for their own purposes. “The Hemi engine makes great use of the available air and that’s been a huge part of the design’s longevity and success,” said Scott Clark.
The Valvetrain Manufacturer’s View
When it comes to the question of who has the toughest job in the manufacturing side of the Hemi drag racing world, we’d argue that valvetrain manufacturers have the most issues to deal with. Wayne Jesel, whose name serves as the basis and foundation of one of the most successful and respected valvetrain companies in existence, agreed.
“Our job is to make the engines live,” he said with a laugh. When we talked about the advancements he has witnessed over his decades in the sport of drag racing, he talked about how material quality and manufacturing developments have advanced the company’s product, but that the challenges were still there.
“Weight is obviously a concern when we talk about high-rpm engines like these,” Jesel said. “For years, steel was the only material strong enough to work, but with today’s available materials and what we can do with things like billet aluminum, we have options to best suit the application.”
“If you had told me 40 years ago that we’d still be developing products for the same engine decades later, I would have laughed. “The Hemi is still hanging in there and it won’t be going anywhere for a while,” Jesel said. “The biggest challenge for us is that the angles and geometry are so challenging on these engines because of the layout of the head and how hard the racers run them—we keep refining and improving our products.” Jesel talked about how continued development in all aspects of the engine has made the Hemi a more effective package over the years. “Top Fuel valvetrain parts are almost antiquated compared to the pieces racers in the Pro Mod and alcohol classes can run,” Jesel explained. “The development work that has been done (and allowed by rules) with alcohol engines have allowed us to have engines that get buzzed to 10,500 rpm during a run and survive. The internal engine parts have come a long way as well.”
So is the Hemi the best drag racing engine ever? “It is a heck of a package and we continue to refine it,” Jesel said. “The thing that’s interesting is that the target is always moving and that’s what keeps the sport of drag racing moving ahead. If it isn’t the best, it is certainly one of the best, that’s for sure.”
The Crew Chief’s Opinion
Billy Stocklin’s name is well known in the world of drag racing. As a leading tuner of Pro Mod cars, radial cars, and someone who has worked his magic on combos of varying sizes, power adders, and performance levels, he brings an interesting perspective to the Hemi conversation.
“In my mind, the Hemi’s biggest strength is its toughness,” Stocklin said. “When you look at how power-adder racing has progressed, the Hemi’s toughness and its ability to get the job done have set it apart. In the late 1990s and early 2000s, the 481X (Chevy style) engine was really popular and it was competitive. The issue that started happening with that engine is that regulations on overdrive caused racers to have to spin the engine higher and higher and the layout of that style engine is just not capable of being spun like that and living through it like the Hemi can.”
Stocklin gives the opposed-valve layout credit for a lot of the Hemi’s strength when it comes to today’s racing world.
“You can spin a Hemi hard enough to keep it competitive with overdrive limits and all and I think the valvetrain layout is part of that. The thing that is interesting is that there are other setups that can make huge power outside of the Hemi. Most of the big nitrous engines out there are wedge-style and they make competitive power, it isn’t that the Hemi is the ultimate for actually making power, but I think it is the best for the environment that it has to work in.”