A brief history:

The word HEMI ™ seems to hold some magical sound to petrol heads in love with the American V8. That didn’t happen by accident, hopefully this story will fill you in on some of the history and details that helped create this iconic brand name. I will start with a brief history of Walter Percival Chrysler as I am sure most Hot Rodders will know little about him. We all know the truths and myths about Henry Ford, but Walter Chrysler also has an interesting story that needs to be told to give a background to what made this company great and developments that lead to the production of the iconic HEMI.

Walter Percival Chrysler. 1875 - 1940

Walter Chrysler followed his father in the engineering side of repairs and maintenance of Steam Locomotives and eventually rose to be plant manager of American Locomotive Company in Pittsburgh at the age of 35. He recognised that the future was in the motor industry and jumped at the offer of taking up the works managers’ role at Buick when it was offered to him, even though he took a 50% pay cut to $6000 a year. His new boss was a man named Nash (sound familiar ?). By 1912 Chrysler had negotiated his salary up to $50,000. In 1917 he became head of Buick on $500,000 a year, a part of that was a share offering making him a wealthy man. He was now well connected in Detroit and recognised as a man with both engineering knowledge and leadership skills.

The auto industry at that time was extremely incestuous and people jumped from brand to brand almost daily. When the Willys Corp got into trouble in 1919 the bankers approached Walter Chrysler to bring the Willys Overland division back to life. Chrysler negotiated the first ever $1 million dollar annual salary package with a 2 year contract. Willys Corp also owned the marine and aviation divisions of Deusenberg Motors at that time and it as there that Walter found his engineering ‘dream team’ of Fred Zeder, Owen Skelton and Carl Breer. He called them the 3 Musketeers. Chrysler signed on at Maxwell-Chalmers as chairman while still at Willys in 1921. In 1922 Walter Chrysler borrowed $16.5 million and bought Maxwell, changed the name to Chrysler in 1924 and took the 3 Musketeers with him.

If Walter Chrysler had known the term Hot Rodder he would have put his hand up as one. Walter and the 3 Musketeers did not test their new engines in a secret location, the four of them would climb into the new car at nights and race at the traffic lights in the streets of Detroit.

As the future HEMI (which is what this article is really about) was to come in 3 brands, Chrysler, Dodge and DeSoto, I should add a little here about the brothers Horace and John Dodge. Theses fortunate folks just happened to have a foundry making transmissions for Oldsmobile when in 1903 Henry Ford wanted to start making cars. Henry offered them 10% of the stock in Fords’ company in return for supplying $10,000 worth on engine castings. From this they drew nearly $10 million in dividends and eventually sold the stock back to Henry for $25 million, not a bad return on $10k in ten years! Unfortunately John and Horace Dodge both died in 1920 in their 50’s before they got to spend it all.

In 1914 Dodge broke away from the Ford relationship and started making their own cars. Chrysler acquired Dodge in 1928 which gave Chrysler a huge foundry and a modern forge for making axles etc, plus a new network of distributors. It also made his company about the same size as Ford and GM, for the first time the Big 3 controlled the majority of the market. This gave Chrysler 500 engineers on the payroll, way more than any of his competitors at the time.

It could appear that Henry Ford deliberately let the others overtake him, he had hung on to the concept of just making one model for way too long. In 1927 the Model T, the only car under the Ford banner, had no service brakes at all, just a band on the tail-shaft operated by the right foot. The handbrake operated rear external drums. It ran magneto ignition and made a shade over 20 HP. It didn’t have a fuel pump or a water pump, and was really hard pressed to compete in all but the cheapest end of the market. Although a more expensive car, Chryslers came with 4 wheel hydraulic brakes from 1926 onwards, and made 68 HP.

1928 was a big year for Chrysler in many ways. On the race track his 72 series roadsters ran 3rd and 4th at Le Mans. Walter also knew that Henry was coming back with the Model A so he introduced the 4 cylinder Plymouth in competition. Walter was so chuffed with his new Plymouth that he took the 3rd car off the line and drove it over to the Ford Motor Co and took Henry and his son Edsel around the block for a test-drive! Plymouth was the only car company to increase its sales every year of the depression and Chrysler Corp came out ahead of Ford in 1933, in fact Ford was relegated to 3rd position for the first time, GM was on top. In 1933 Chrysler sold a total of 385,666 cars, 249,667 of them Plymouths compared to the total for Ford of 334,969. This was a disaster for Henry after making 5 million Model A’s between 1928 and 1931. At least this was improvement over 1932 when sales virtually dried up for all the car makers. Ford only made 232,135 cars in 1932, and 26 of Fords’ 32 assembly plants were forced to close.

In 1928 Walter had also acquired Dodge but already had plans in place for a car to target Dodge if his take-over was not successful. He could have cancelled this but let it go ahead letting DeSoto sort it out with Dodge in the market place. DeSoto was introduced in the 1929 year model and at first Dodge was above DeSoto, but in later years it went the other way. The name DeSoto comes from the Spaniard who explored the south east of the USA coastline and named the Mississippi River in 1539. The name Plymouth came from Plymouth Rock where the pilgrims in the Mayflower first arrived in the USA. The brand names Plymouth and DeSoto were cleverly chosen and well accepted. Now he had the full set of brands. Just to top it off he started Fargo Trucks that same year, but that’s another story.


Even though the depression was just around the corner, on September 19th 1928 Chrysler ordered work to start on the magnificent Art Deco Chrysler Building in New York City. Walters’ new headquarters would be the world’s tallest building, but only for 11 months before being surpassed by the Empire State Building in 1932. This building was not a project of Chrysler Corp, it was Walters private investment for his children. At a cost of $20 million he obviously had very deep pockets in 1928 !!  It is still the worlds tallest brick building, and in anticipation of the newly released Plymouth, Walter had the gargoyles shaped like the Plymouth radiator cap. The American public loved anything BIG and this drew attention once again to the Chrysler Brand, another marketing masterpiece during what was a miserable time for many people.


The Gargoyles on the New York Chrysler Building are fashioned out of stainless steel to look like the Plymouth radiator cap.

At the end of the war in 1945 the US auto industry started converting factories back to passenger car production. Chevrolet, Chrysler and Ford went back into production still using engines that were more than a decade old and sadly out of date, but none of them seemed in a hurry to change. Engineers at Oldsmobile changed all of that when they took the new 135 HP 303 cu in OHV V8 Rocket engine designed for the larger cars, and stuffed it into a body not much bigger than a Chevy of the day. The 1949 Oldsmobile Rocket 88 was the car that started the race to the Muscle car era that was to follow.



Left.  49 Olds Rocket 88                                Right. 53 Hudson Hornet

NASCAR was founded in late 1947 and in 1949 the new Olds Rocket 88 won 6 of the 9 races in the Strictly Stock Division, renamed  Grand National in 1950. This division was for cars exactly the same as you could buy at the dealers and it was quickly learned that whatever won on Sunday sold on Monday.

Surprisingly Hudson shared the glory with the Olds Rocket 88. The Hudson Hornet had a huge 308 cu in flathead inline 6 with twin carbies and had a body that was streamlined and sat about a foot lower than all the competition. This seemingly boring old flathead 6 won 27 of the 34 NASCAR Grand National races in 1952, followed by 22 of 37 in 1953, and 17 of 37 in 1954.

With Hudson and Oldsmobile winning all the races, Ford, Chrysler and Chevrolet were apparently being left behind. In the background however the engineering team at Chrysler was working hard on prototypes. Ford still ran the old flathead until 1954, and Chevy was stuck with the Blue Flame 6 until 1955, all producing way less than 100 HP.

In 1946 Chrysler engineers looked at producing their own OHV engine as they knew Cadillac and Oldmobile were doing the same and didn’t want to be caught out. During the war Chrysler produced their first hemispherical combustion chamber (HEMI) engine which was a huge 2500 HP 36 litre inverted V16 aircraft engine with HEMI heads. The valves were operated by a single overhead camshaft and the prop shaft was gear driven from the centre of the engine. This prototype engine was both super-charged and turbo-charged and it first flew in June 1945 fitted into a P47 Thunderbolt and powered it to 504 mph. The war ended before it went into production.

At 122 inches long the inverted V16 Chrysler Hemi was a big engine.

The engineers at Chrysler collected a variety of engines from around the world to study and found that HEALY in England had built a twin cam 4 Cyl HEMI. This engine produced the highest horsepower per cubic inch of any engine they had experimented with. At first the Chrysler engineers were told to build an inline 6 with a HEMI head but the valve train was too weak and complex to mass produce so they went back to the drawing board.  In 1948 the Head of Engineering William Drinkard suggested that they build a 330 cu in HEMI V8 and that idea really set a cat amongst the pigeons in head office, but eventually the project was given the green light.

It would hardly be right to go past this point without mentioning the work of Zora and Yura Arkus-Duntov with their ARDUN hemi-head conversions for the 1947 Ford flathead truck engine. (ARDUN is made up from their last name). Secrets were hard to keep in the auto industry and it is unlikely that the ARDUN design escaped the notice of the Chrysler engineers, or was it the other way around ?  The ARDUN also has two rocker shafts and a very similar valve and head layout to the Chrysler HEMI. Designs similar to this can also be found in race cars of the 1930’s in Europe so it is hard to say where it all originated and it is known that Chrysler had been playing with the concept in 1939. Zora went broke making the ARDUN and later did some remarkable work at Chevrolet and has been called the father of the Corvette.


Ardun internals                                               The Ardun

The ARDUN Hemi design was later produced in Brazil from 1966 to 69 as the SIMCA (a division of Chrysler) based on the smaller Ford V8-60 engine block. A very interesting mix of brands and designs indeed ! This little 147 cu in engine made 130 HP.

The Simca-Ardun Hemi

The development of the Chrysler HEMI was not without its problems and camshaft and valve-train failure was the major ones to be overcome. Finally they came up with an oversquare design with a bore of 3.8125 in and a stroke of 3.625 in. It came with hydraulic lifters, water heated two barrel Carter carburettor, shot peened forged steel crank and twin point ignition. It made 180 HP, the most powerful V8 engine available by far in 1950.

Performance features of the  HEMI engine design adopted by Chrysler were
a) High volumetric efficiency.
b) High thermal efficiency, low specific heat rejection.
c) Superior combustion characteristics.
d) Excellent adaptability to higher compression ratios.
e) Lateral valve arrangement, greater valve durability.
f) Superior manifolding available due to the valves being close to the opening of the port.
g) High valve lift.
h) High mechanical efficiency.

The early HEMI was a heavy engine, mostly because of the huge cast iron heads that have large castings to hold the complex rocker gear. Its worth noting is that the combustion chambers on these engines had to be machined and therefore the improved and more even volumetric efficiency added to the power.


The 180 HP 1951 Hemi Firepower 331.         Early 392 in a 53 DeSoto

The Chrysler HEMI Firepower was first introduced for the 1951 model year, and at first only in the luxury full size cars. In July 1951 Chrysler built the Saratoga Club Coupe based on the far smaller Windsor chassis and this car just knocked the doors off the Olds Rocket 88.  The HEMI won its first NASCAR races in 1951 and claimed the NASCAR Championship in 1954. The Hemi was popular at the track and was also selected as the INDY PACE CAR for 1951, 54 and 56.

The new HEMI had not escaped the notice of a young Don Garlitts, and Don writes that he was sure the poster advertising the HEMI at 180 HP should have read 108 HP, and was pleased to discover he was mistaken. Don grabbed a HEMI from a wreck and put it in his 39 Ford coupe that he used to tow his flathead V8 powered dragster. One day at the track he was sitting there disheartened with a blown gearbox so decided to give the coupe a run, and was blown away by the fact that it was only 2 seconds slower than the dragster. Dons wife said ‘why not put the HEMI in the dragster’, and the rest is history. On November 10, 1957, Don Garlitts drove his Swamp Rat 1 Chrysler Hemi powered dragster to 176.4 mph in 8.78 seconds to become the fastest man in drag racing and the first over the 170 mph mark.

Don Garlits with the final incarnation of Swamp Rat 1

Three different series of HEMI V8 engines have been built by Chrysler Corp since they first introduced the FirePower HEMI  in 1951. The Firepower HEMI stared life at 331 cubes and grew to 354 then finally they produced a 392 cubic inch version in which they raised the block height by half an inch. This was the most powerful and the best of them came fuel injected making 390 HP from the factory.  They only made 16 of these and all but one was recalled and converted back to dual 4bbl carters.

Desoto also had a Hemi called the Fire Dome of a very similar design but it was smaller at 276 cubes and was in fact shorter between the bore centres. Just to confuse the issue Dodge had another version called the Red Ram starting life in 1953 at 241 cu in and this was a shorter engine again.

DeSoto 276 HEMI                             Dodge Red Ram HEMI, the smallest of all.

Chrysler and Dodge and Plymouth introduced the Poly head engine in 1955 and these share some engine naming identifications with the HEMI. A RED RAM or SUPER RED RAM could be either a Poly or a HEMI, depending on the year. The POLY engine was designed to take advantage of the HEMI design but only has one rocker shaft, and therefore has some compromises. The valves were diagonally across from each other rather than directly opposite. They were cheaper and lighter than the HEMI. The poly engines are easy to recognise by the wavy design of the valve covers and the spark plugs are on the outer side of the engine. As these are not recognised as being the real deal HEMI, I will not expand on them further.

All of these series of early HEMI engines have the distributor at the rear and the well known plugs down the centre of the valve covers. Interestingly Plymouth missed out on a Hemi in those years. Overall there are 3 different block lengths and 12 different displacements in this first series of engines and it can get very confusing trying to be sure you have parts for the correct version. HEMI block castings prior to 54 have the bell housing cast as part of the block, the newer blocks did not have this making it easier for Hot Rodders to adapt other transmissions as after 1954 they all have the same bolt pattern.

I searched the web and a lot of the books that I have and came up with this listing of the passenger car engines.  has a database full of details including all of the truck, marine and industrial engines. Also worth a look are and

 Sequence Year Name C.I. H.P. Torque HP / cu in Bore Stroke Comp ratio:1 Dry weight lbs Carb. BBL
 CHRYSLER:   Bore Centre 4.5625    
C51 - 8 - 1001 1951 Chrysler 331 180 312 0.54 3.8125 3.6250 7.50 710 2
C52 - 8 - 1001 1952 Chrysler 331 180 312 0.54 3.8125 3.6250 7.50 710 2
C53 - 8 - 1001 1953 Chrysler 331 180 312 0.54 3.8125 3.6250 7.50 710 2
C541 - 8 - 1001 1954 New Yorker 331 180 320 0.54 3.8125 3.6250 7.50 710 2
C542 - 8 - 1001 1954 New Yorker 331 180 330 0.54 3.8125 3.6250 7.50 710 4
WE55 - 1001 1955 New Yorker 331 250 340 0.76 3.8125 3.6250 8.50 729 2
NE55 - 1001 1955 New Yorker 331 250 340 0.76 3.8125 3.6250 8.50 729 4
CE55 - 1001 1955 Imperial 331 250 340 0.76 3.8125 3.6250 8.50 729 4
3NE55 - 1001 1955 C300 331 250 345 0.76 3.8125 3.6250 8.50 735 2-4V
NE56 - 1001 1956 New Yorker 354 280 380 0.79 3.9375 3.6250 9.00 737 4
CE56 - 1001 1956 Imperial 354 280 380 0.79 3.9375 3.6250 9.00 737 4
3NE56 - 1001 1956 300B 354 280 385 0.79 3.9375 3.6250 9.00 737 2-4V
NE57 - 1001 1957 New Yorker 392 325 430 0.83 4.0000 3.9060 9.25 767 4
3NE57 - 1001 1957 300C 392 325 420 0.83 4.0000 3.9060 9.25 767 2-4V
CE57 - 1001 1957 Imperial 392 325 430 0.83 4.0000 3.9060 9.25 767 4
58N - 1001 1958 New Yorker 392 345 450 0.88 4.0000 3.9060 10.00 767 4
58C - 1001 1958 Imperial 392 345 450 0.88 4.0000 3.9060 10.00 767 4
58N3 - 1001 1958 300D 392 380 435 0.97 4.0000 3.9060 10.00 767 2-4V
n/a 1958 300D 392 390 435 0.99 4.0000 3.9060 10.00 767 Fuel inj
DESOTO:   Bore Centre 4.3125      
S17 - 1001 1952 Firedome 276 160 250 0.58 3.6250 3.3440 7.00 629 2
S16 - 1001 1953 Firedome 276 160 250 0.58 3.6250 3.3440 7.10 629 2
S19 - 1001 1954 Firedome 276 170 250 0.62 3.6250 3.3440 7.50 631 2
S21 - 1001  1955 Fireflite 291 200 274 0.69 3.7200 3.3440 7.50 631  4
S22 - 1001  1955 Firedome 291 185 245 0.64 3.7200 3.3440 7.50 631 2
S23 - 1001 1956 Firedome 330 230 305 0.70 3.7200 3.8000 8.50 669 2
S24 - 1001 1956 Fireflite 330 255 350 0.77 3.7200 3.8000 8.50 669 4
S24A - 1001  1956  Adventurer 341 255 375 0.75 3.7812 3.8000 9.50 669 2-4V
S25 - 1001 1957 Firedome 341 270 375 0.79 3.7812 3.8000 9.25 669 2
S26 - 1001 1957 Fireflite 341 295 375 0.87 3.7812 3.8000 9.25 669 4
S26A - 1001 1957 Adventurer 345 295 355 0.86 3.8000 3.8000 9.50 669 2-4V
 DODGE:   Bore Centre 4.1875      
D44 - 1001 1953 Red Ram 241 140 220 0.58 3.4375 3.2500 7.00 590 2
D50A - 1001 1954 Red Ram 241 140 220 0.58 3.4375 3.2500 7.10 590 2
D50 (1, 2, 3) 1954 Red Ram 241 150 222 0.62 3.4375 3.2500 7.50 590 2
D551,D552 1955 Super Red Ram 270 193 245 0.71 3.6250 3.2500 7.60 600 4
D553 - 1001 1955 Super Red Ram 270 183 245 0.68 3.6250 3.2500 7.60 600 2
D500 - 1001 1956 D 500 315 260 330 0.83 3.6250 3.8000 9.25 611 4
D500-1  - 1001 1956 D 500 315 295 na 0.94 3.6250 3.8000 9.25 611 2-4V
KD500 - 1001 1957 D 500 325 285 345 0.88 3.6875 3.8000 9.25 611 4
KD500-1   - 1001 1957 D 500 325 310 350 0.95 3.6875 3.8000 9.25 611 2-4V


All of Chrysler’s HEMI V8 engines have the inlet valves placed in the head towards the centre of the block close to the inlet manifold which are easy to operate with a simple push-rod design. The exhaust valves are way over the outside of the engine and sit at an extreme angle (almost horizontal) making the design of the rockers very complex. This is why the engines are so wide and have such huge valve covers.

If you look at the list above there is one weird engine size. The 1957 345 cu in DeSoto engine is the 341 high-deck series engine with a 0.020 increase in the bore gaining only 4 cubic inches. You would have to ask if this was intended or just a way to get rid of some mistakes. These are listed as ‘very rare’ and I suspect that they may have had some blocks that were unusable as standard bore for maybe a casting or machining error, but cleaned up ok with a set of 020 thou oversize pistons so they were sold as a special version.

What I find remarkable in the 7 years from 1951 to 58 is that these engines nearly doubled the available HP per cubic inch. The 1951 version made 180 HP from 331 cu in which is 0.54 HP per cubic inch and in 1958 the rare Fuel Injected version made 390 HP from 392 cu in, ever so close to the magical ONE HP per cubic inch.

If you look at the chart above you can see that the significant changes were in compression ratio and improved breathing. Octane Ratings for fuel available at the pump also significantly increased from 79 in 1946 to 99 for premium in 1958. It should be noted that prior to 1972 HP was usually measured as Brake HP, and when tested most of the accessory belts were disconnected and tubular exhaust headers were used. Today they use Net HP where everything is hooked up as per factory.

Sadly Chrysler found lighter and cheaper ways to make HP and the first generation of the passenger car HEMI came to an end in 1958 after just 7 short years, but left a mark that would last for another 60 and more.

2nd generation HEMI.

In 1966 Chrysler re-introduced a second version of the HEMI and it only came in one size, 426 Cubic inches and fitted with dual Carter AFB 4 bbl Carbs. This engine made a fair bit more than the factory stated 425 HP 472 Ft lb torque and was really a NASCAR engine that was fitted to street cars to qualify them to use it for racing. Only 11,000 were actually sold between 1966 and 1971 but thousands more were made for racing and are still produced to this day. There is too much already written about this engine so I have not included it in this article.

2nd Gen 426 with factory 2 x 4 bbl squeezed into a 68 Barracuda.

3rd Generation HEMI

Chrysler never forgot the value of the HEMI brand name, in fact it’s a registered trade mark, and once again took advantage of peoples fascination with it by introducing the 3rd Generation HEMI in 2003. At first it came out with the 5.7 (345 cu in) rated at 345 HP, ONE HP (net) per cubic inch. In 2009 it was upgraded with newer head designs and variable valve timing and now the current 5.7’s comfortably make 390HP/ 402 ft lb of torque.

From the factory they are a good looking engine. This is the 6.1 (370 cu in)

Lots of accessories are now available for this Gen 3 HEMI and can be stroked to 426 cu in easily.

There have been two further upgrades to this Mexican made engine being the increase to 6.1 in 2007 and then in 2011 another increase to the 6.4 or 392 cu in version. The best looking of all of these is the 6.1 with its striking alloy intake manifold, all of the others have plastic intake manifolds.  The 6.1 makes an easy 425 HP 420 ft lb of torque and the 6.4 /392 makes 470 HP with 470 ft lb of torque.

The latest version on the drawing board will be a supercharged 6.2 due out in 2015 rated at over 500 HP. There are also crate versions of this new engine displacing 426 cubes if you have a fat enough wallet.

This 3rd generation HEMI is unique in that it runs twin plugs fired from coils mounted directly to the valve covers as it needs a lot of spark to fire these engines. The latest HEMI combustion chamber is not quiet a perfect HEMI as pollution standards needed to be met. In the bottom end below the new HEMI incorporates some race car stuff that you would not expect such as a windage tray, roller cam followers, cross-bolted mains, and oilers facing the load side of the bores. These engines are not heavy boat anchors like the first two versions of the HEMI, they are thin-wall lightweight blocks with alloy heads weighing in at 590 lbs, about the same as a small block Chev or Ford. Size wise the blocks are also very similar but the heads then hang out the sides making them about 2 inches wider each side. Otherwise they are a strong powerful lightweight compact modern engine with lots of potential to the Hot Rodder looking for something different. They respond well to a bit of tweaking and can easily make more than 500HP and remain very driveable.


On the left is the combustion chamber of a 426 Funny Car Hemi, and on the right is the new 5.7 Hemi, as you can see, not a perfect Hemi but it works pretty much the same.

Making these engines run is simple and cheap. You don’t need to go out and buy an aftermarket ECU and try to make it work, all you need to do is use the 2005 Dodge Ram PCM (Power-train Control Module) and hook it up (with some exceptions). Chris Squire at makes wiring harnesses and re-programs the PCM.

I have installed one of these new 6.1 HEMI engines with a Dodge Ram 5-45 5 speed auto in my chopped and stretched 34 Chrysler Limo and will continue with an article about these engines when I have some more photos and have sorted out the serious issues.


Others have been having fun with the new HEMI too.

Damn fast BBQ !

5.7 HEMI powered trike

The new HEMI in a snow plough !


 ■ Rob Muston