Why the SRT8 is no hemi-powered Challenger

The automotive world is seemingly in a full-body tizzy over the return of the Dodge Challenger. Hitting dealerships now, the SRT8 version has been the darling of the automotive press for months.

I’ve gone on record plenty of times about Dodge’s horrible belated timing — just like the 1970 Challenger on which the lines are almost completely based. And though I haven’t yet had the opportunity to slam the Challenger SRT8’s sickening 4000-plus pound curb weight, I’ll simply say that it’s disgusting and move on to a more important topic.

Dodge says its Challenger is equipped with the “6.1 liter SRT Hemi® V8 Engine.” Hear this loud and clear: no SRT8 Hemi Dodge or Chrysler is a hemi. With full credit to former Vice Presidential candidate Lloyd Bentsen, I say: “I knew Mopar’s Hemi, and you, Mr. SRT8, are no hemi.”

In an effort to make it crystal clear, ladies and gentlemen, since 2002 there has been a difference between “Hemi” (the marketing brand name) and “hemi” (the technology from which the brand got its name.)

The word “hemi” (lower case) is short for hemispherical combustion chambers. Put into terms the average runway model might understand, a cylinder fitted with a head utilizing a chamber formed like a hemisphere makes the quickest, largest, and most efficient boom. Placing valves on opposing sides of a central spark plug provides maximum ability to introduce air/fuel, ignite it and remove resulting exhaust and heat. This means more power, a happier driver, and busy radar-wielding police officers.

Chrysler Corp wasn’t even close to the first producer of an engine with hemispherical combustion chambers. The famous Hemi engines of the 1960s and early 1970s weren’t even Chrysler’s first hemi engines in name or technology.

So let’s start the history lesson: Way back in 1902, the Welch brothers of Pontiac, MI began building cars with an overhead cam engine featuring hemispherical combustion chambers. By the time General Motors bought out Welch (then known as Welch-Detroit) in 1911, the cars had yet to go into production. Tragically, GM decided to do nothing with the engine technology.

Charles Knight built his 1904 Silent Knight prototypes, which used a sleeve-valve engine with hemispherical heads. Like Welch, Knight never went into series production, but unlike GM, Daimler purchased the technology and used in its later products.

Starting in 1908, Franklin started using a hemispherical design on its air-cooled production engines, making it the first true production hemi. A well-known manufacturer of cutting-edge luxury cars since 1902, Franklin made hemi-powered cars available to its well-heeled customers, which included Charles Lindbergh and Amelia Earhart.

In 1912 Peugeot’s factory racer, featuring a three-liter hemi-headed mill, dominated European events. Other companies would soon develop their own competing hemis. The most notable company was Alfa Romeo, whose chief designer, Vittorio Jano, created four, six and eight cylinder dual-overhead-cam hemis (some were even supercharged) for race and road cars starting in 1925.

Possibly the most unorthodox early hemi came from BMW’s 1937 328 sports car. Engineers utilized vertical pushrods and rockers for intake valves, but to actuate the exhaust valves located on the opposite side of the head, vertical pushrods and rockers pushed a second set of horizontally placed rods and rockers. Although complex, it worked surprisingly well, plus the dual rocker boxes made the inline overhead valve six look like a dual-overhead-cam unit.

Three years after Jaguar’s XK DOHC six became the first post-war hemi, Chrysler finally got into the game with 331 cubic inch FirePower-equipped 1951 New Yorkers and Imperials. De Soto’s 276-ci FireDome appeared in 1952 and Dodge’s 241 ci Red Ram V-8 came in 1953. Mopar “baby hemis” could also be found in Cunningham sports cars and Facel Vega grand tourers.

The heavy, complex baby hemi engines ate valve springs for lunch and camshafts for dinner. In 1957, Chrysler decided to end production of the engine with the 310-hp 325-ci Dodges and 345-hp 345-ci De Sotos. Chrysler held out through 1958 with the 380-hp 392-ci hemi in the 300D.

Then came the 426-ci Hemi. Debuting in 1964 factory-supported racers, the engine redefined the reaches of performance in NASCAR and drag racing. Chrysler begrudgingly made the 425-hp street Hemi available in 1966 to meet homologation rules. (Homologation is the fancy word used to describe the requirement in a production-based racing series that anything offered on a race car is also sold in dealerships to non racing clients.)

Mopars powered by the so-called 426 “Elephant motor” became legendary purely on brain-bruising performance. Simple hot-rodding easily unleashed over 750 hp. Due to being as fuel efficient as a 747, environmentally friendly as Clean Air legislation penned in Houston, maintenance-free as a runway model, and easy to insure as a sky-diving octogenarian, it was killed off after 1971.

With original Hemi cars bringing over six figures at auction and a contemporary power war raging, DaimlerChrysler decided the time was right in 2002 to bring back the Hemi in modern Dodge, Chrysler (and gulp) Jeep vehicles. Consumers responded by opening up their checkbooks and lines of credit.

The ads might have asked “that thing got a Hemi?”, but in reality, none of the Dodge and Chrysler engines based on the modern 345-ci “Hemi” can be considered a “hemi”. Plain and simple, none of these engines, base and SRT8 Hemi offerings included, actually have hemispherical combustion chambers! Just because they have valves opposing central spark plugs does not necessarily indicate that there is a hemispherical combustion chamber formed inside.

It is easy to get lost in the technology and terminology. The bottom line is that the SRT8 delivers 425 horsepower and 420 pound-feet of torque, which absolutely is better than the quoted statistics for the 426 when normalized for the difference between pre-1972 gross and ’72-on net SAE ratings. There is simply no arguing: the SRT8 Hemi is a fabulous engine, and the use of Hemi as a brand name was a stroke of product marketing genius.

But for me, when it comes to dropping this glorious 6.1 lump in a 2008 Challenger weighing more than a 1970 Hemi Challenger, the lack of Pistol Grip four-speed, and the lack of accuracy in marketing, I can only come to one conclusion:

The SRT8 Challenger might look like a Hemi Challenger…but really it’s just a semi-hemi.


25 Responses to Why the SRT8 is no hemi-powered Challenger

  1. BTW That “Jaguar’s XK DOHC six ,… the first post-war hemi” also had a SIX DECADE lifespan, from the late 1940s until the mid 1990s. It powered everything from Le Mans dominating race cars (C-type & D-type), to legendary sports cars (XK 120/140/150 & E-type), sedans and saloons (Mk 1-Mk X, XJ, S-type, etc), Limos (Daimler Sovereign & DS420), and even military hardware such as tanks and APCs! (Scopion, & Scimitar)


    You are right though, the “Hemi’s” of today are just poseurs.


  2. As long as Chuck spotlights the topic of British hemi engines, it seems an appropriate opportunity to point out that not all hemi engines were extremely potent. While the Jaguar XKs (especially in C and D Type forms) were amazing performance vehicles, the Daimler SP250 “Dart” was a terrible dog. Even with hemispherical combustion chambers, the SP250 was slow, sloppy and (dare I say) downright ugly. I’ve always thought of the SP250 as England’s Packard Hawk, except with a fiberglass body and hemi engine instead of rust-prone steel and a supercharged (non-hemi) engine.

  3. While I’ve seen a few Darts, I’ve never looked closely at them. Do they sport a Rover V8, or did they source a MOPAR? Or was it their own creation?

    Not that I really care that much. 😉


  4. Wow, I never thought I’d see the day when there was something about British sports cars that Chuck didn’t know!

    The SP250 Dart was the first to utilize a new Daimler-specific 2548cc over-square pushrod V8. This was the same engine to go into the Daimler version of the Jaguar MKII through 1969. It produced about 140 gross hp.

  5. Joe Dokes says:

    While your history is largely correct, you miss a few key points of hemis in general and the the Gen III hemi in particular.

    First, no modern “hemi” is truly a hemi, they all make compromises that make the combustion chamber less than a perfect 1/2 a sphere. What makes a hemi is both the approximate shape AND the fact that the cantered valves pull away from the cylinder walls as they open. Unlike say a traditional small block Chevy head in which both the intake and exhaust valve is at least partially shrouded by the cylinder wall, the cantered valve design allows for much better breathing.

    Thus, when one examines the GEN III Hemi, it becomes clear that while it’s combustion chamber is less of a sphere than either the 392 or 426, it still has a general spherical shape, it is just a 1/4 of a sphere rather than half a sphere.

    Finally, you can see the power of the Gen III Hemi when you compare it to GM’s or Ford’s modern engines, the Hemi puts out more hp per liter than either of these.


    Joe Dokes

  6. Joe,
    While you are absolutely correct, the point still holds true — the modern Hemi is in name only. The name Hemi is from the hemi of hemispherical. Of first Latin, then Greek, “hemi” means “half” and hemispherical specifically means half of a sphere.

    No matter how much Mopar fanatics and Chrysler marketing teams shout, one-quarter of a sphere doesn’t qualify as hemispherical. Since no other company is trying to claim that their modern engines’ combustion chambers are hemispherical for marketing reasons, that leaves Chrysler standing alone.

    And I always find it amusing that when I discuss this issue offline, the topic of how great the Gen III Hemi is compared to Chevy or Ford. It could be the greatest engine of all time, but that doesn’t remedy the fact that it is a Hemi in marketing brand name only.

    But even your last statement doesn’t seem to hold true. The GenIII makes 425hp from 6.1 liters in top form for 69.67 hp/liter. Chevy offers
    438hp from 6.2L in the standard Vette Coupe/Convertible for 70.65hp/l and in the Z06 it’s 505hp from 7 liters. (72.14 hp/l). Then, of course, there’s the upcoming ZR1, which gives 620hp from 6.2L (courtesy of a supercharger.) This equates to 100hp/l.

  7. David Lee says:

    Neither the “early hemi” nor the 426 engines had true hemispherical combustion chambers. So that isn’t the test. all three have dual rocker shafts servicing the int and exh valves. So it may be. All have different angles of inclination to the bore centerline. All three have different centers of divergence of the two banks of valves, most pronounced in the ’26 style.
    The production 26 exh port was bloody awful, a product of the need to be be able to fit the engine between the frame rails of the then current b-body front sub-frame to run in nascar. Just look how drastically they are reworked in the SSAH cars.
    The ports in the new hemi are vastly superior on both sides to the production 26 examples. AJP, Brad’s Fatheads and ICH RA heads all have substantially reworked designs from production. The first two would make crappy street heads. You could drive a bus down those things! = no mixture velocity at low rpm. But nobody would deny that they are hemis too. Yes , the Gen III does have a double quench area spanning the portions of the circumference of the chamber between the valves but there’s nothing wrong with that, and it’s no accident. It promotes better turbulence in the end gas, allows a higher compression ration with a MUCH smaller dome, and ergo better flame travel and a much, much lighter piston and rod assembly. It was no accident that they used 5/8 and 11/16 rod bolts instead of 3/8 on the nascar and A-990 cars. Even then, they knew heavy was bad. They just had no choice.

    It is going to need reworked rocker arms to allow seriously high lift cams and/or taller and larger diameter valve springs. Once they hit the market, look the blank out!! The 6.1 cannot accomodate any taller than 600 lift now, even with aftermarket H-11 material springs. Stand BACK when it can! The new dominator is right around the corner. Remember, the current 426 versions from ICH are making an easy 565 horses with minor porting, but with all the inherent first design geometric limitations still in place. The new (09) 5.7 heads are actually better than the 6.1s in terms of volumentric efficiency, wait til the 6.1s get the upgrades, with their larger valve sizes. Yowee! – DL HouTX

  8. Rob Adcox says:

    The original 426 Hemi WAS a true hemispherical engine. And the blogger is right: the new “hemi” is more akin to the boss 429 Ford engine in its combustion chamber design. Note the crescent shape.

  9. Dan says:

    Everyone seems to have forgotten that ma mopar designed a monster of an aircraft engine in WWII that was a true hemi. And if you want to get really picky the gen 1 was far more of a “true” hemi than the 426. In fact this same argument was conveyed when the old timers saw the new 426 design. “oh hell that’s not a real hemi” All in prospective I guess. Is the gen III a real hemi? No of course not. But it is a mastery of marketing.

  10. d cook says:

    Real Hemi–Not real Hemi.
    Real Lips–Botox Lips.
    Real Boods–silicon Boobs.
    What does it matter as long as the job gets done?
    The 3 generations of Hemis have been the dominant race engine for sixty years, except when outlawed by various cowardly sanctioning bodies. If it ain’t got wide chrome valve covers with4 plug wires down the middle, its hard for me to take it seriously. If you’ve ever heard one wail across Bonneville early in the morning, you’d know what I’m talking about. 50% nitro and 20% blower overdrive will awaken the speed demon that lurks in all of us.

  11. Claude Conn says:

    I have been a mechanic since the 1950’s. I have worked on car, motorcycle and aircraft engines. You are mearly argueing semantics. Although the engine, it is surely not a motor, (semantics again?)does have quench areas on both sides of the valves, it is still a hemispherical combustion chamber. And really, will it affect life, as we know it?
    Thanks for you time,
    Claude Conn

  12. Rob Adcox says:

    Calling it a Hemi for marketing purposes is fine, but when auto journalists can’t discern between hemispherical combustion chambers and semi-hemispherical chambers, I feel compelled to respond. Either it’s a hemi or it isn’t. And to Dan, the 426 hemi had true hemispherical chambers.

  13. M Harris says:

    I don’t see what the fuss is, one way or the other. I own a Challenger SRT8 and like the Mazda commercials, it goes ZOOM, ZOOM.

  14. Tom says:

    Wow, what a mopar hater!!!

  15. Kevin says:

    Thanks to all of you who have posted here with your vast knowledge of the “hemi”. I recently purchased a Ram 1500 (2011) and it sounds, accelerates and moves like the a bat out of hell. I love my “marketeted hemi”. It looks beautiful (deep water blue pearl) and i would put it up against the ford raptor, chevy what ever and for sure the Toyota Tundra iForce. This truck and engine kick serious “mopar” ass. I understand the only thing on it that is mopar is the oil filter. That is ok with me.
    Thanks again for the insigt.
    Kevin, Littleton, CO.

  16. Matt Bugsby says:

    Interesting rant. I agree with what Tom says about “MoPar Hater” (has he maybe seen too many MoPar tail lights?) , and with most of the other comments posted.
    I’m curious as to when Chrysler ever claimed to have made an engine with “half a circle” as a combustion chamber, let alone when they claimed to have made the first one. So why the irrelevant history lesson? The early engine was advertised as a “dual rocker shaft”. I think the term “hemi” was coined by others and later adopted by Chrysler, much like “Chevy” and “Vette”. As far as being “complex”, the ONLY extra part is that second rocker shaft. A SOHC is much more “complex”.
    What Chrysler DID do was to offer this well-engineered, well-built engine to the average American car buyer in the 1950s for a reasonable price. Comparing a Dodge Red Ram to a Jaguar is sort of like comparing strawberry shortcake to Savoy Truffle. So what?
    The statement about the Red Ram eating camshafts and valve springs is a straight-up lie. I’ve seen these engines in Dodge trucks with many, many miles and nary a valve train problem. With high-lift cams, maybe, but not in stock form.
    Adapting the the 1950’s “hemi” head to the stout RB block to create the 426 was simply a common-sense step using recycled technology, and of course masterful engineering. Not bad for the smallest and poorest of the Big Three. The resentment is still there 45-plus years later. Oh well. I’m not aware that the 426 “hemi” was any more high-maintenance than any of the other muscle cars of that era. If you want to talk “runway models”, let’s go back to the Jaguar and other British makes.
    Then, the Gen III “hemi”, like a bad rash to some, it comes back AGAIN. There goes that irritation again, and the predictable editorial slamming. Does it have a “half-circle combustion chamber”? Heck no, nor has any practical automobile engine ever had. Chrysler owns the word, and could slap in on a redone 273 if they wanted to (oh, sorry, I meant “4.5 Liter”)
    I saw a recent Engine Masters challenge where a Gen III won, the nearest two competitors were Chevies. So much for advertised power-to-displacement claims. On top of that, both Chevies had aftermarket blocks and/or heads, the Gen III had reworked stock pieces. Isn’t it irritating? I guess there are still a few good engineers around. I think it’s a great engine, has a lot of potential, and as far as the Challenger, we’ll see. If nothing else, it makes a good truck engine. And it’s fun just to say “hemi”, because it irritates some people! “Hemi, Hemi, Hemi!!” there, irritated enough? Good!

    • Charlie Marshall says:

      I agree! This guy is obviously more anal than a liberal IRS agent! My new Dodge has a HEMI and I could gives a rats ass what this loser said!

  17. username17 says:

    In that case, I’ll just say I love my 440 Six Pack Hemi. Hey, who cares as long as it accelerates like a bat outta hell, right? Had a great summer mowing my lawn with my Briggs & Stratton Hemi too.

  18. Keith says:

    Yep, like much of everything we do today. BIG on the “Hemi” name, but NO Hemi. Who’s pulling who’s chain here? If it don’t have true hemispherical combustion chamber design, it’s NOT a Hemi. The name “Hemi” today seems to be used more as a model brand by Chrysler today, and there are a lot of people driving these things that have no idea of what a real “Hemi” was. Go back to the early 1950’s & look at a Chrysler FirePower engine. Then go look at that so called “Hemi” lump that’s under the hood of your so-called “Hemi”.

  19. Matt Bugsby says:

    To quote from the original post:
    “So let’s start the history lesson: Way back in 1902, the Welch brothers of Pontiac, MI began building cars with an overhead cam engine featuring hemispherical combustion chambers. By the time General Motors bought out Welch (then known as Welch-Detroit) in 1911, the cars had yet to go into production. Tragically, GM decided to do nothing with the engine technology.”
    Even more tragically for GM owners, Chrysler did…3 different times! Now, all GM owners can do is quibble about the name. Whatever.

  20. Required says:

    This is simple. I shouldn’t have to dumb it down: the engineering is very good. The problem is that calling something what it isn’t is lying. Aw hell. I’m done arguing with morons. I know what a hemi is. Too bad Chryasler marketing can fool you folks so easily.

  21. Charlie Marshall says:

    It’s a HEMI turdhead whether you like it or not. Plugs down the center of the head along with opposing valves even if the angle fails to suit you. Get over it!

  22. Yes, Charlie, it is a HEMI ™…it’s just not a hemi.,,whether you like it or not.

  23. guest says:

    This history lesson was fascinating to me. Long ago, I used to work on rotary engines, and I was researching what “hemi” means. I got more than I bargained for — and loved it. Thanks, Sam

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