Classic cars forum & vehicle restoration.

[Uncle Joe]

After getting permission to do so, I posted this yesterday or the day before as a reply to another topic. Then thought that it warrants a topic of its own.

Time to be educated dudes and dudettes! Before anyone says it, yes, history is boring....

A Brief History of the Development of the Chrysler Hemi Engine

Contrary to what some may think, the hemispherical head engine concept did not emerge fully developed under the hood of the first Chrysler 300 in 1955. Chrysler had begun development of two industrial sized hemispherical headed engines during World War II; a V-12 for application in tanks, and a V-16 for the aircraft industry. Flat out, the aircraft engine pushed the huge P-47 Thunderbolt war plane along at 504 miles an hour. Speculators at that time said that the V-16 was making at least 3,000 horsepower, but actually it produced closer to 3,500.

At the end of the war, Chrysler engineering now knew how good the hemi heads could be. Chrysler, however, whose name is synonymous with the hemi, was not the first company to test or use the Hemi heads on an engine. It was the design of choice for many famous automakers. Miller racing, Duesenberg, Stutz, and of course Offenhauser had all made use of hemi head design.

Working in engine development were James Zeder, Ray White, John Platner, Mel Carpentier, William Drinkard, and Ev Moeller, one of the first graduates of the Chrysler Institute in 1939. These men tested virtually every hemi head engine they could find in every combination possible. One engine that truly stood out for power and efficiency was in the English Healey, a small passenger car. It had twin camshafts located in the block, operating push rods for the overhead valves in the hemispherical combustion chambers. It was a long stoke, small bore engine, but made the most power for its size of any engine they had tested.

Engineer John Platner found that the hemi was displaying characteristics opposite established doctrine. It eliminated knocking, and had superior volumetric and thermal efficiency. With a compression ratio of 7.0 : 1 the hemi beat the L-head, which required a compression ratio of 10.0 : 1 to achieve the same results. The overhead valve arrangement was somewhat better, but suffered from losses in volumetric efficiency and premature valve wear. It was clear that the hemispherical heads were superior to all else. The intake valve was situated close to the manifold and carburetor. At an angle of 58 degrees across the top of the combustion chamber, the exhaust valve allowed magnificently efficient burnt gas releases. Because of this, the heads extended valve life, aiding in effective uniform valve stem cooling and valve seat cooling inside the chamber.

Armed with this information, James Zeder decided to test the head on one of Chrysler's existing 6 cylinder engines. A double overhead camshaft system driven by a dual chain was made to accommodate the hemi combustion chamber. Once that was done and certain modifications were made to the Chrysler 6, it was installed in a Chrysler car.

The test vehicle went to Wallace Zierer, who was in charge of road test conditions. Zierer reported significant power increases. The engine ran easily on the 80 octane fuel that was standard for the time. Roughness, which was the current theory about hemispherical heads, just did not exist under any condition. The hemi head 6 cylinder engine actually being smoother than the flathead 6 cylinder, with a nearly undetectable level of noise and vibration at idle speeds.

By 1948, the engineers had a 330 cubic inch 90 V-8 hemi running in the laboratory. Designated the A182, this engine was exclusively used on a dynamometer to evaluate its performance and characteristics. After many tests, Chrysler management gave the O. K. for an engine of this size and type to be designed for production.

Mel Carpentier's department built the prototype V-8. Designated model A239, it had 331 cubic inches and was shorter and lighter than the A182. It was also built to specifications laid down by William Drinkard, head of engine development, who set down some very tough parameters. He wanted a 100,000 mile engine and would accept nothing less. No major parts, such as bearings, valves, pistons, and rings, were to require replacement at less than 100,000 miles.

One major obstacle was premature camshaft wear. It was Chrysler's first attempt at a production overhead valve engine. They were not familiar with valve loading, which caused the area between the valve tappets and the camshaft lobe to wear very quickly. Some of the prototype engines failed right in the engine plant. Clearly they wouldn't have gone a 100 miles, let alone 100,000. Bob Rodger, later to be head of development of the 300, was called in to solve the wear problem. Eventually the highly skilled engineers resolved the camshaft wear issue under Rodgers’ leadership. A change in the tappet material and the method in which the face of the tappet was formed, a graphite coating , and an additive in the engine oil settled the whole issue.

Another major hurdle was how to accomplish spark plug changes without taking off the valve covers. This was resolved by using a steel tube that went through the valve cover, a long ceramic boot over the spark plug, and an o-ring to seal the tube against the head to prevent oil leaks. The spark plug tubes and wires were put underneath a cover that had the wires exiting at the back of the engine which gave the new V-8 a clean look.

Other engine improvements included shot peening of the crankshaft to improve fatigue life and having it machined to remove tool marks and surface roughness. The tappets were hydraulic to enhance quiet, smooth operation, as well as to ensure valve life through constant control of opening and closing. Carter Company developed a water jacketed carburetor with an integral automatic choke to insure that the new engine would not stall nor develop ice. A dual breaker ignition was developed to insure constant, hot sparking while maintaining a reserve of ignition voltage.

Finally, after over 8,000 hours of dynamometer testing and more than 500,000 miles of road testing, the new V-8 was ready for production. Along the way, the new engine had been designated "Fire Power." So certain were the management team of the success of this engine that some months into the testing of the Fire Power, orders had been sent to DeSoto and Dodge to submit proposals for a hemi V-8 of their own.

Introduced in the fall of 1950 as a 1951 model, the Fire Power V-8 was offered as on option in the Saratoga, while it was standard in the New Yorker and Imperial. The Fire Power was an oversquare engine in that the bore was larger than the stroke. With a bore of 3.81 inches and a stroke of 3.63 inches, it measured 331.1 cubic inches. The intake valve was 1.81 inches. Positioned 58.5 degrees across the hemisphere was the exhaust valve that was 1.5 inches in diameter. The valves were actuated by push rods operating rocker arms riding on twin shafts. The crankshaft rode on 5 main bearings.

The pistons were designed to be able to slip between the crankshaft counterweights at the bottom of the stroke, thereby achieving a much smoother running engine with less friction and slower wear characteristics. The engineers also built the Fire Power to run with slower piston speeds which ensured long piston and ring life. The block was relatively light, short and rigid. With a two barrel carburetor it made 180 horsepower and 312 foot pounds of torque. The introductory compression ratio was 7.0 : 1. Some criticism was leveled at the weight of the engine, in particular the weight of the cylinder heads. A single hemi head weighed 119 pounds.

From the very start, performance was paramount. Someone convinced Chrysler management to put the Fire Power into a Saratoga Club Coupe, the lightest body manufactured by Chrysler. Released in July of 1951, the Fire Power Saratoga Coupe was a first shot response to Oldsmobile’s 1950 installation of their V-8 in an 88 Coupe. The Saratoga was fast; it would do zero to 60 in 12 seconds flat, beating Cadillac's 13.5 second run and Olds' 12.5 second time. It ran the 1/4 mile in 18 seconds at around 82 miles an hour right off the showroom floor.

In March of 1952, V. P. James Zeder and his team presented a "white paper" to the Society of Automotive Engineers. Right after the meeting he was mobbed by what he called the "hot rod" boys, who were very enthusiastic about the idea of getting maximum horsepower out of the Fire Power. Zeder was intrigued with what they had in mind, and performance testing commenced on the Fire Power. While the testing progressed, Zeder kept in touch with his adopted gang of "hot rod" boys. He listened to and passed along their suggestions on how to make the hemi faster.

The first investigation involved two areas for increased performance: compression ratio and volumetric efficiency. Using high compression pistons, compression ratios of 7.5 : 1, 10.0 : 1, and 12.5 : 1 were tried. Nothing else on the engine was changed. The 12.5 : 1 pistons achieved a 15 % increase in horsepower over the 10% increase with the 7.5 : 1 pistons, which translated into 228 horsepower. But it would run only on aviation gasoline of 130 octane, which was not commercially available to the public.

The next area involved volumetric efficiency. The stock exhaust headers were replaced with streamlined units which increased torque from 312 foot pounds to 330 and horsepower to 193. Gaining confidence, they explored other areas for improving volumetric efficiency: the valve ports, intake manifolding, carburetors, and camshafts.

The hemi heads had plenty of room for larger valves. The ports were smoothed and opened up .125 of an inch on the exhaust and .25 of an inch on the intake. For manifolding and carburetion, engineers developed a set of 4 inline, single barrel carburetors, each feeding two cylinders. They also experimented with different grinds on the camshaft. As it happened, the electronic computer was newly introduced, and Chrysler Corporation was one of the first companies to utilize computer generated computations to achieve the maximum out of the camshafts it was testing.

The test engine, designated as the K-310, responded well to the modifications. In the first run with a slightly hotter than stock cam, the high flow heads, and the standard flow carburetion system, The Fire Power achieved 225 horsepower and 332 pounds of torque. With a mid range camshaft, which gave the best all around performance, the hemi made 275 horsepower and 352 pounds of torque. In the final test, a high performance camshaft and the four carburetor manifold combined to make 308 horses with torque of 361 foot pounds. Finally, the 12.5 : 1 pistons were reinstalled to produce a devastating 353 horsepower and 385 foot pounds of torque.

Personally satisfied, Zeder wrote of the tests that "the basic Fire Power cylinder gives performance comparable with Indianapolis engines, which have been developed for power without regard to any other purpose." In conclusion, he stated: "we remain unalterably convinced that, in the battle of the combustion chambers, the spherical segment chamber has demonstrated unquestionable supremacy."

In 1952, DeSoto introduced its version of the hemi head V-8. It was a 90 degree design of 276 cubic inches and was rated at 160 horsepower. It resulted in 50,000 installations. While smaller, the DeSoto V-8 had all the same characteristics of the Chrysler Hemi. The third and final version of the original hemi design was introduced by Dodge in late 1952 as a 1953 model. It was a 90 degree design of 241 cubic inches that was rated at 140 horsepower.

In 1953, an engineer who had become a key member of William Drinkard's team made a proposal that Chrysler build a car around a high performance Fire Power that had excellent handling and unique styling. It was taken seriously, very seriously. Bob Rodger was instrumental in seeing the Chrysler 300 come to life.

Outside of Chrysler Corporation, the Fire Power was used in racing and as power plants for other car makers. Briggs Cunningham was one builder who saw the potential of the hemi head engine. His goal was to win the 24 hour race at LeMans. To qualify, he had to build 25 cars. He received some technical information assistance from Chrysler, but engine modifications were done solely by him with non factory parts. He raced his cars for three years, and retired from the circuit in 1955. He did race in LeMans in 1952, finishing fourth, a remarkable first effort.

James Zeder was immensely proud of the hemi engine and wanted to see it used in racing applications. He had an eye on the Indianapolis 500, the greatest spectacle in racing at the time. He had the lab begin experimenting with the 331 Fire Power. John Platner and Don Moore were deeply involved in building the "Indy" engine which was called A311. It was built with 8 Hilborn fuel injectors, big valves and ports, streamlined big exhaust manifolds, and a modified camshaft. Under the guise of testing tires for Firestone and Goodyear, the engine was installed in an Indianapolis special racer. With the A311, it ran the same lap speeds as the Offenhauser and Miller racing machines.

The A311 was put to the test again in June of 1954. Shortly after the running of the 1954 Memorial Day 500, Chrysler dedicated its Chelsea proving grounds. The first four finishing Indy drivers were invited to bring their racers over to christen the 4.7 mile long oval race track. With wide lanes and banked curves, the drivers were able to hold their cars wide open all the way around. The single fastest lap that day was made at 179 miles an hour. Then the Kurtis Kraft tire test car with the hemi A311 screamed by the centrally located pits and timing stand at 182 miles an hour, then did it twice more. Zeder and his engineers were delighted. They knew that a stock block engine with push rod technology could easily compete at Indy and, most likely, easily win.

Unfortunately, news of the test was given wide publicity. In a flurry of activity, the engine size rule was changed to a 272 cubic inch limit for stock engines. A slight decrease in piston stroke easily achieved the 272 cubic inches, but down on power, the hemi didn't qualify. It would not be the last time that rules were changed by sanctioning bodies when Chrysler came out to play.

The 1954 model year saw the first stages of performance improvements in the hemi engines from the Corporation. Chrysler Fire Power V-8s now had 195 horsepower by bumping up the compression ratio to 7.5 : 1. As well, it had another version with a four barrel carburetor that put out 235 horsepower.

One of the biggest advances in automotive history was introduced in January 1955. It should have come as no surprise since Chrysler had already built a 300 horsepower engine from the 331 Fire Power in 1951, used in the K-310 concept vehicle built by Ghia in Italy. In 1952, a similar engine had powered the Ghia built C-200.

January 7, 1955 was the date that dealers were allowed to place the C-300 on their showroom floors. It was an absolute marvel. The show rooms were jammed all day long and every day thereafter for a whole week.

Bob Rodger's suggested concept in 1953 came through as he had envisioned it. The new C300 was the first production car to have 300 horsepower, the hottest thing on wheels at that time. It wasn't inexpensive either, with a base price of $4,035 compared to a fully loaded Plymouth that could be had for $2,246!

To achieve 300 horsepower, Chrysler followed established performance techniques. High flow heads with larger, cleaner ports and valves operated from a special camshaft through solid valve tappets, with compression of 8.5 : 1. Dual exhaust and two four barrel carburetors completed the package. The 300 was totally reliable, required no real special effort to operate, delivered a smooth but firm ride, and had some of the best brakes in the entire industry.

In one of the first road tests of the C-300, Tom McCahill, writing for Mechanix Illustrated, wrung out the big Chrysler. He was effusive in his praise. He consistently got to 60 miles an hour in under 10 seconds. Out of his several timed runs, his average was 9.8 seconds. He put the C-300 on a certain highway that he used and got up to 130 miles an hour before he ran out of road. He wrote about that by stating: "it was as strong as Grant's Tomb, and 130 times as fast."

On the beach at Daytona, a completely stock C-300 confirmed Uncle Tom's finding by posting a 128 mph timed run. It was the fastest vehicle there, taking top speed honors. Tim Flock, driving a C-300, won the NASCAR Championship. All fitting tributes to the engine that Chrysler advertised as "the most powerful production car built in America" with "the greatest, safest power in any American car."

The 1956 Fire Power continued to be at the head of the horsepower race. The 331 was bored out 0.130 of an inch which gave an increase in cubic inches to 354.06. The camshaft specifications remained the same as did the valves. Compression was raised in an altered set of heads to 9.0 : 1. The exhaust manifolds were changed to encourage higher flow rates. It gave the 300B a rated horsepower of 340. Additionally, an optional set of heads that were installed at the dealer level bumped the compression ratio to 10.0 : 1. That gave the 300B a 355 horsepower rating. It also made it the first production engine to exceed one horsepower per cubic inch. Tom McCahill was again enthusiastic about the 300, calling it "motorized dynamite, a connoisseur's car not meant for timid driving" and "Unmatched in a class by itself." McCahill, who owned several 300s, praised the suspension and handling qualities of the 300B by adding: "these cars hunker in to a corner like a starving dog clamped on a bone." The engine wasn't all there was to the 300: he called it the "best handling car I have ever driven straight from the showroom." Over several timed runs, Uncle Tom got an average 0 to 60 mph times of 8.2 seconds.

With the new 355 horsepower V-8, the 300B allowed Chrysler to again clean up the beach at Daytona. It set a new record of 139 miles an hour. Tom McCahill pointed out that running on wet sand was not a good way to determine speeds. His own speed tests on a dry asphalt road got very near 140 miles an hour with the 340 horsepower engine. Buck Baker cleaned house and won the NASCAR championship with a 300B.

In 1957, the Fire Power was boosted again in displacement to 392 cubic inches. In standard form it belted out 325 horsepower. For the new 300-C, the output went up to 375 horsepower. Higher compression heads made 390 horsepower. Along with new bodies came torsion bar suspension, and the ultimate in automatic transmissions, the Torqueflite.

Tom McCahill whipped the big car from 0 to 60 mph in an 7.8 seconds. On his "private" public highway, he made 140 miles an hour. He praised the handling due to the torsion bar set up, claiming that it "set into a groove better than a needle on a record." He said that the 300 series were a collection of "beautiful brutes" suggesting that they were for "hairy chested drivers." He went on to describe the driving experience as about as "subtle as wearing velvet boxing gloves."

With the 300C, Chrysler again lead the way at the Daytona Speed Week. However, performance was off, with the fastest 300 making a one way run of 138 miles an hour. At first the Chrysler engineers thought that the beach surface, which varied from year to year, was the culprit. Certain that they had a 145 mile an hour car, they took the same car to the Chelsea Proving Grounds outside the Chrysler Headquarters. Opened up on the 5 mile track, the 300C only made about 140 miles an hour. The driver reported a heavy wind whistle at high speed. Finally, it was recognized that the windshield trim stuck out nearly an inch, making it a very effective air brake. Using clay, they formed the top of the windshield into a smooth, clean shape with no edges. The same car went back out and ran 146 miles an hour.

In 1958, the fierce growl of the hemi was about to be silenced. The 300D had the same engine as the 300C, except the D was rated at a standard 380 horsepower. Experimenting with fuel injection, Chrysler had Bendix build an electronic system that produced 390 horsepower from the 392 hemi. It was troublesome and only 16 cars had it installed; allegedly all were changed to carburetors by Chrysler.

The manufacturing process for the 1958 engine run had also changed. The hardened crankshaft was replaced by a drop steel forged unit. The optional "chassis package" was not offered, and the rear axle ratio options were drastically reduced.

At Daytona Speed Week, the 300D was obviously not what the earlier marques had been. It won the flying mile but was beaten by Pontiac for top speed, although the Pontiac was still not up to the 139 mile an hour mark set by the 300B in 1956. Tom McCahill still called it "America's best sedan." He could whip the 300D to 60 in 9.0 seconds. It was a sign of the times in that the 1957 and the 1956 could outrun the 1958. The "D" managed a top speed of 135 miles an hour.

For 1959, Chrysler Corporation no longer offered the hemi in its Chrysler marque cars. However, the hemi wasn't quite gone yet; the standard engine in the Crown Imperial was the 325 horsepower 392 hemi V-8, but that was the end of the line for the first generation Chrysler hemi engines. Highly prized today in both collector cars and as race engines, the legendary hemi continues to make news and set records.

[pigtin]

You mention Briggs Cunningham. I recently bought a couple of DVDs called 'A Gentlemans Motor Racing Diary': a compilation of films taken at various racing circuits in the fifties by John Tate. A great deal is devoted to Briggs Cunningham's le Mans attempts.

[Uncle Joe]

I read a little about Briggs lately myself. Its a bit surprising that he isnt better known to most people, especially as he was involved with some of the british greats, such as Stirling Moss and Mike Hawthorn...

[Scotty]

Good stuff UJ - thank you!

[Uncle Joe]

You are more than welcome Scotty.

I like automotive history, maybe I should come over one time and help you a bit at the museum....

[Old-Nail]

Interesting history UJ thanks for posting.

[Scotty]

[peter scott]

[Uncle Joe]

That question has been up to debate for quite a long time. One thing is for certain, it wasnt Chrysler.

There are other things as well that nobody seems to know who was first with as well, disc brakes, 5 valve heads, oval pistons....

[Scotty]

Hi UJ,

This may be of interest - in the August edition of The Automobile there is going to be an article on "The Chrysler Hemi" by Sandy Skinner. I don't know if you get the magazine in your neck of the world, but if you do it comes out on the third Monday of the preceding month (21st July).

If you can't get them over there PM me and if you'd like to read it I'll photocopy it and send it over - that is providing I can get one at the newsagents, they can be a bit hit-or-miss some months!

Scotty.

[Uncle Joe]

Scotty, thanks for the offer, its very kind. British magazines are very difficult to get over here.

Hows your Chev coming along? Have you started the engine work yet?

[Scotty]

Not yet - currently the plan is to strip it down, have a good rummage around in the top end, decide what needs done, decide what extra I can do (and afford) and then rebuild.

The most cost-effective route is buying what's needed when we go back to the US in October. I can pre-order a lot of it through my friends company South East Chevys based in Orlando, so it'll be waiting for me to bring back home. Doing it this way means I can buy twice as much for my £, if not even more as I'm cutting out the UK middle man and / or the shipping charges if I bought it here. Of course the down side is I have to wait, but that's no problem, anything worth doing well can't be rushed.

That's this weeks plan, next week it'll be different!

[Uncle Joe]