The people behind GM's new Gen V LT1 are arguably the finest engine-design team in Detroit, so it's fitting that their latest technology leader would make its debut in the '14 Corvette Stingray. The LT1 isn't just an enhanced LS3; in fact, the two engines share very few parts. If all you do is compare raw numbers, you'll miss the biggest part of the story.
The LS3 was a fine engine with plenty of untapped potential. In basic form it delivered 430 horsepower at 5,900 rpm and 424 lb-ft of torque at 4,400 rpm. The new LT1 delivers 455 hp at 6,000 rpm and 460 lb-ft of torque at 4,600 rpm. Plugging that additional output into a vastly improved drivetrain, suspension, and structure enables the Stingray to deliver sub-4-second 0-60 times. If the LT1 is used as a foundation for Z06 and supercharged ZR1 models, as is expected, we have a lot to look forward to. But before getting into some of the LT1's details, let's take a look back at the original 1955 small-block Chevy engine to see how far we've come.
Chevy's first small-block V-8 was nicknamed the "Mouse Motor" for its diminutive size. The all-cast-iron engine weighed in at 531 pounds, displaced 265 cubic inches, and made 165 gross hp in its basic two-barrel-carb configuration. The Corvette version with a Carter four-barrel made 195 hp. These numbers reflected "gross" horsepower, measured using a bare engine with no accessories installed. GM's engines have been measured using "net" standards, with all accessories installed, since 1972 to better reflect real-world conditions. Calculated the old way, the LT1 might well have made 500 horses.
The all-aluminum LT1 weighs 66 pounds less than the 265 SBC and produces 290 more hp. Comparing fuel-mileage figures is a little more difficult. By 1957 the fuelie 283/283 was the top-performing engine available in a Corvette, with fuel efficiency of around 12 mpg. The EPA city/highway rating for the new LT1-powered Stingray is 17/29. There were no emissions ratings in '55, but you can be assured that the two mills are worlds apart in that area as well.
The LT1 design team started work in 2007, with 30 analysts working on computer models for three years before the first mule engine was built. As outlined in VETTE's two-part story, "Getting To Know The LT1" (April and June '13), there were approximately 19 parts assemblies with dedicated design teams for each one. Each component system was carefully analyzed for efficiency and coordination with the others.
The major breakthroughs for the LT1 include direct injection, Active Fuel Management (cylinder deactivation), continuously variable valve timing, and a radically new combustion chamber that enables an 11.5:1 compression ratio. To test the new LT1, special dynos were built so that an engine could be tilted up to 53 degrees to simulate cornering forces as high as 1.3 g. The high-speed, high-load torque sessions were even more grueling: Test motors were run at full throttle from 0 to 120 mph using simulated transmission shift points, and this cycle was repeated nonstop for hundreds of hours. (You'd almost think the engineers were developing a race engine…)
While the new Stingray is more than just a powerful engine, the "systems model" used in the LT1's development was also employed on the rest of the car. The basic structure is often described as feeling like it's made of granite. The car's center of gravity is just 17.5 inches, and an electronic differential keeps the tires glued to the line of a curve without any of the instant breakaway behavior exhibited by the previous Z06. And thanks to the extra grunt available earlier in the rpm curve (90 percent of peak torque is on tap from 3,000 to 5,500 rpm), the C7 Stingray runs just a tick behind the C6 Z06 in a straight line.
Gone are the days of the easygoing 327/250 base Corvette. Today, all Vettes are stump pullers. And with the "entry-level" Stingray running 0-60 in just 3.9 seconds, the upcoming performance models have quite a foundation on which to build.