DETROIT -- The great-great-grandchild of the first Corvette V-8 promises to be one powerful prodigy.
Seen through the misty lens of automotive nostalgia, the 450-horsepower LT1 engine under the hood of the 2014 Corvette could be considered the latest update of a classic -- the 58-year-old small-block Chevy V-8. In reality, it's entirely new, though it shares a handful of dimensions and some basic design features with that classic engine, the 265-cubic-inch Turbo-Fire of 1955. Chevrolet uses those links to its advantage, marketing the latest engine as the fifth generation of the small-block family.
The longevity, racing successes and hot-rodder appeal of the first-generation, small-block V-8 -- a high-revving 195-horsepower replacement for the tepid in-line 6 that had served the Corvette since its 1953 debut -- created a durable legacy. The engine overcame the inherent limitations of its pushrod -- or as Chevy calls it, camshaft-in-block -- configuration and has held its own with more modern designs.
Like the original small-block V-8, the new LT1 uses two valves per cylinder, actuated by pushrods, rather than a dual-overhead-cam four-valve design. That has spurred criticism from enthusiasts who say the car should use the latest technology (and who may have forgotten that the Corvette offered a twin-cam V-8 in the 1990s). Whether the naysayers are right will have to wait until the new engine's final figures for performance and efficiency are tallied.
In a presentation to the news media last fall introducing the new engine, Tadge Juechter, the Corvette chief engineer, said that abandoning the pushrod V-8, and with it the small-block heritage, had been discussed. Contemporary designs, including a turbocharged twin-cam V-6, were considered. But "that wouldn't be a Corvette," he said.
Jordan Lee, chief engineer for the new small-block V-8, said the reasons for sticking with the pushrod engine were not purely emotional. An overhead-cam engine would have to be four inches taller than the existing engine -- and would not fit under a Corvette's hood.
Here are highlights of the engines that led to the newest Corvette power plant:
GENERATION ONE The new-for-1955 V-8 greatly improved on the heavy V-8 engines of G.M.'s Cadillac and Oldsmobile brands. The cylinder block was unusually compact, with the iron casting refined to reduce thickness and weight. The intake and exhaust passages were large for the era, and the valvetrain was relatively light. The engine woke up the Corvette, which was on the cusp of a body redesign as well.
The horsepower crown for the first-generation engines was the fuel-injected 327-cubic-inch version of 1964, at 375 horsepower, followed by the 1970 LT-1 350, at 370.
But the small block's history is a tale of interrupted success. The output of the 1982 350-cubic-inch small block had dwindled to a meager 200 horsepower, five more than the 1955 engine (though the measurement standard had changed to net horsepower from gross output). Engine design progressed little during the '70s and early '80s when engineers were overwhelmed by the challenges of pollution-control regulations.
GENERATION TWO The second-generation small-block had its premiere in the 1992 Corvette, reviving the LT1 name and generating 300 horsepower. With a revised cylinder-head design and reverse-flow cooling, this engine departed from the first-generation architecture. The most potent version was the 330-horsepower LT4 of 1996.
GENERATION THREE A third-generation small block arrived in the 1997 Corvette. This was an all-new engine that shared little more than its surname with grandpa. A deep-skirt block -- not as compact as the original design, but stronger -- was specified. Aluminum took the place of cast iron, making the new engine almost 100 pounds lighter than its smaller ancestors.
More important, the cylinder heads were redesigned to allow for evenly spaced exhaust and intake ports, improving air and fuel flow. The 2001 385-horsepower LS6 became the first small block to exceed the advertised output of the 1964 engine.
GENERATION FOUR The next version, a potent 400-horsepower 6-liter, arrived under the hood of the 2005 Corvette. It was similar to the previous generation, with minor revisions made to accommodate variable valve timing and increased displacement. Chevrolet reduced the engine's valvetrain weight with the introduction of titanium intake valves. Most powerful of the fourth-generation engines was the 2009-13 Corvette ZR1's 638-horsepower supercharged 6.2-liter.
GENERATION FIVE With the arrival of the 2014 Corvette, G.M. saw a need to upgrade the engine technology. Contemporary combustion science and direct fuel injection had much to offer, setting the stage for what is effectively a new engine.
The redesign emphasized improving the combustion process. The positions of the valves were modified, with exhausts and intakes swapping location, and the combustion chambers were redesigned. The spark plug was relocated, the piston tops were reshaped and most significantly, fuel injectors were installed in the combustion chambers.
Direct injection, a technology that has a long history in diesels and is prevalent in today's best gasoline engines, allows precise timing of fuel delivery and enhanced control of burn, while cooling the combustion area. That allows more cylinder pressure, which translates to more power and efficiency. While many direct-injection engines use turbocharging to attain high cylinder pressure, it's achieved here with a modest 11.5:1 compression ratio.
Variable camshaft timing complements the combustion-control scheme. Managing intake and exhaust valve opening and closing can tailor an engine's torque curve to best meet driving needs. For the LT1, Chevrolet opted to control intake and exhaust events simultaneously, rather than independently, which would have entailed far more complexity. According to Mr. Lee, the gains were 80 percent of what would have been possible had Chevy elected to control the intake and exhaust cam timing independently.
Final figures have not yet been published, but a horsepower rating of at least 450 is expected, with 450 pound-feet of torque. That's 20 more horsepower and 26 more pound-feet of torque than the fourth-generation 6.2-liter produced. More significantly, much of the torque gains are said to be at low engine speeds, resulting in a more flexible, more responsive engine.
Fuel economy estimates are not available, but G.M. said it expected better mileage than the current engine delivers. The highway number will be aided by Active Fuel Management, which shuts down four cylinders at cruising speed and will be offered for the first time in a Corvette.
If the past foretells the future, stouter versions of this standard-equipment engine will be offered in other Corvette models, and already G.M. has shown versions of the new V-8 family destined for trucks. If the current supercharged 6.2-liter were to realize approximately the same gains as the naturally aspirated engine, we could see a 670-horsepower Corvette ZR1 down the road.
Not bad for a little pushrod engine.
This article originally appeared in The New York Times.