'There's a ton of hoopla surrounding all things Hemi these days, and for good reason. While we can live without the investor types who revel in dollar signs instead of burning rubber and seven-grand power shifts, the Hemi renaissance-on the dragstrip, on the collector scene and in the show room-signals incredible times for horsepower junkies of all persuasions. You see, in the nearly half-decade since 2003 when Chrysler rekindled its Hemi legacy in the form of those potent 5.7- and 6.1L rear-wheel-drive trucks and cars, the war planners over at Ford and GM have been forced to take notice-and up the ante-just as they did in the '50s and '60s.
The winner in all of this is the consumer who can now choose from more showroom stock horsepower and performance than ever before. Don't believe it? Then check into the specs of halo musclecar offerings like the Z06 (505 hp), GT500 KR (540 hp) or anything from the SRT8 family (425 hp with much more on tap) and you'll see bigger net horsepower ratings than even the biggest guns of the musclecar era. Beyond that, even the bread-and-butter light truck, SUV, and RWD V-8 passenger car consumer has more net horsepower to choose from than ever before. Heck, even the mainstream 5.7L Hemi is good for 340-350 horsepower (depending on tune). And remember, this is all net horsepower of the real-world variety. Not pie-in-the-sky, under-ideal-conditions popcorn like we used to get in decades past. So our hats go off to Chrysler for throwing another log on the fire and feeding the frenzy that continues to grow.
Some interesting parallels can be drawn between the new Hemi and the very first generation of Hemis that arrived way back in 1951. Back then Chrysler (and the rest of Detroit) was looking for a modern engine to carry its products into the postwar era. The mood was optimistic and everybody knew cars would be getting more luxurious and heavier with each passing season. Competing OHV V-8 designs generally employed strategies that banked heavily on the assumption that gasoline quality and supply-and octane rating-would continue to escalate, thanks to wartime advances made in petroleum refining and formulation.
As such, most of these post-WWII OHV V-8 designs-the '49 Olds 303 and Cadillac 331, '52 Lincoln 317 and Studebaker 233, '53 Buick 322, '54 Ford 239, '55 Packard 352, Pontiac 287 and Chevy 265 and '56 Nash 250-were built with the idea that they could rely on future compression ratio increases to add power as the market demanded it. Their (mostly) wedge-shaped combustion chamber designs were dependent on a steady diet of ever-increasing octane numbers to support compression-ratio growth. But over at Chrysler, the emphasis was on efficient breathing first, high compression second.
The original '51-'58 Chrysler...
The original '51-'58 Chrysler FirePower Hemi (Gen I) utilized cast-iron heads with fully machined 109cc combustion chambers, centrally located spark plugs, and an included valve angle of 58.5 degrees. Flat-top pistons delivered 7.5:1 compression. Note how the valves open toward the center of the bore away from the shrouding effects of the cylinder walls, and double rocker shafts actuate the valves.
Former Chrysler director of engineering and research James Zeder outlined the Chrysler strategy in a 1952 SAE report titled "New Horizons in Engine Development." He wrote, "The power of an engine should be based on physique, not on stimulants." In other words, the Chrysler design effort focused on volumetric efficiency and anti-detonation characteristics instead of sky-high compression to make power. By orienting the valves laterally within a hemispherical combustion chamber, the stems tipped outward so that when they opened, the valves plunged into the centers of the cylinder bores where they were not shrouded by the cylinder walls. This arrangement also paved the way for efficient ports with gentle short-side curves that also help flow. Of course this strategy can result in a particularly wide engine package and the expense of a double-rocker-shaft arrangement to actuate the valves. But at the time, low engine weight and compact girth weren't top priorities.
Unveiled in the '51 Chrysler line, the 331ci FirePower Hemi was an instant success. In mild two-barrel form it cranked out 180 hp, 20 more than its closest competitor, the 160hp wedgehead Cadillac 331. In the following seven years, the FirePower grew to 354 cubes (1956), then to 392 cubes (1957), and output of the top-dog, dual-quad 300D more than doubled to 380 hp by 1958. What's more, Hemi fever spread to DeSoto in 1952 with the 276ci Firedome and to Dodge in 1953 with the 241-cube Red Ram. The interesting parallel between then and now is that these Gen I Hemis were installed by the hundreds of thousands into everyday passenger cars and trucks, just like today's Gen III Hemis are. Sure, there were muscle models like the Chrysler 300, DeSoto Adventurer, and Dodge D500, but again, Hemi power was everywhere and you didn't have to spend much extra to get it.