Where to begin? First off, it's common knowledge among those who know the story behind Chrysler's original hemi engine that the engineers chose the hemispherical combustion chamber because it was the most efficient of that day. With a centrally located spark plug, flame travel was equal across the area of the chamber and piston top. A true hemispherical combustion chamber is not a pentroof or any other hybrid shape: It is a true hemisphere. The angle of the intake and exhaust valves in the original design allowed for maximum flow.
The original Chrysler hemi was far from "mediocre" in performance. Even before Chrysler itself decided to exploit the performance potential of this engine, others did. The bread-and-butter hemi was introduced in 1951 and that year a hemi-powered Chrysler Saratoga came in first in the Stock Car Class and second overall in the Carrera Pan-Americana road race. Also in 1951, one of the all-time great American racers, Briggs Cunningham, chose the Chrysler hemi to power his Le Mans race cars. Cunningham continued to use the hemi in his racers throughout the 50s. He won Sebring in 1953, and placed 3rd at LeMans in 53 and 54. In 1952, a hemi-powered Kurtis Kraft Indy roadster was banned from the race during qualifying because it was too fast. In 1953, Lee Petty finished 2nd in NASCAR championship points with his hemi-powered Dodge.
It wasn’t until the introduction of the 300 in 1955 that Chrysler started playing on the performance angle of the hemi. The 331 CID engine in the 1955 Chrysler 300 produced 300 HP. The car was named the "300" because this was the first time a production car had been produced by any of the Big Three that came with this "magic" horsepower number.
In 1956, the 331 was increased in displacement to 354, and in the 300B of that year was rated at 340 HP. Compression was raised from 8.5:1 to 9:1 in the standard engine, and optional 10:1 heads could be ordered which increased output to 355 HP. This was the first production engine to reach the magic "one HP per cubic inch." A lot of people erroneously think the 57 Vette with the fuel injected 283 rated at 283 HP was the first, but it wasn't. The 56 Chrysler 300B was.
Carl Keikhaefer and his team of factory-backed 300s literally dominated NASCAR in 1955 and 56, winning both the road course and the flying mile at Daytona both years. Of the 45 NASCAR races in 1955, the Chrysler 300 won 23 of them. At the Daytona Flying Mile competition that year, the 300 won with an average speed of 127.58 MPH. In 1956, the 300 won again with an average speed of 139.373 MPH, with a maximum one-way run of 142.9 MPH.
When Virgil Exner debuted his 57 designs that completely blew the rest of Detroit away, the original hemi reached its peak in size: 392 CID. Horsepower was 375 @ 5200 RPM. Chrysler no longer officially sponsored the 300 in racing, but that didn't keep individuals from racing the 57 300: a hemi-powered Chrysler 300 won the Dayton flying mile with a speed of over 147 MPH.
The last year of production for the original Chrysler hemi was 1958. In the 300D of that year, fuel injection was offered for the first time and horsepower was at 390 with a 10.5:1 compression ratio. That year, a Chrysler 300D set a Class E speed record at Bonneville when it ran 156.387 MPH.
The hemi engine that Chrysler produced and sold in various Dodge and Plymouth models in the 60s was NOT a redesign of the original hemi. Chrysler used the basic 426 big block wedge engine and designed a set of hemi heads for it. However, because the engine was not designed from the ground up as a hemi, going this route meant the angle of the intake and exhaust valves was not optimum and the combustion chamber was not a true hemisphere (though it was very close). This engine was a MONSTER horsepower producer, however, and more than one “insider” at Chrysler at the time reported that the published HP figure of 425 on the street version was “wildly conservative,” with the true number being “somewhere around 500.” When Richard Petty debuted the race version of the 426 Hemi at Daytona in 1964, he not only won the race, he lapped the entire field. There was literally nothing in NASCAR that year that could even approach the performance level of the hemi. A hemi-powered car placed 1st, 2nd, and 3rd, at Daytona that year, and hemi-powered cars won 26 of the 62 NASCAR races in 64. In 1965, NASCAR officials banned the hemi from competition, but the hemi would return to racing in 1967 when Chrysler built the “street” version of the 426 hemi to get around the 1965 NASCAR ban. In 1967, Richard Petty won 27 Grand National races in his hemi-powered Plymouth, 10 of those in a row.
I think a lot of people who want to dismiss the current hemi as a lot of marketing hype are too young to remember the reputation the original hemi had in the 1950s and the reputation the 426 hemi had in the 1960s. One advantage the new hemi has is that it was designed, just like the original, from the ground up as a hemi. The very thing that makes a DOHC design such an efficient power producer (the overall shape of the combustion chamber) is the highlight of the modern hemi. And yet a pushrod engine is cheaper to build than a DOHC engine, so you get the best of both worlds with a true hemi that is a pushrod design. In “standard” trim the new hemi is already producing as much horsepower as the LS1 in the C5 Corvette. Chrysler hasn’t even begun to tap into this engine yet, and I predict with very little tweaking it will be putting out well over 400 HP in later iterations from Chrysler. Stay tuned.
[ April 14, 2004, 12:02 PM: Message edited by: G-Man II ]
