The SAE-certified numbers are in. Now it's official: The 6.2L LS9 engine developed for the new Corvette ZR1 makes 638 hp at 6,500 rpm and 605 lb-ft of torque at 3,800 rpm. That makes the LS9 the most powerful production engine ever offered by the Detroit Three. Given the times, this event strikes us as a hot rod miracle. We were expecting maybe another new hybrid or a hot E85 turbo four-banger. But a supercharged V-8 with nearly 650 hp? How does an engine like that even happen in this day and age?

GM Executive Vice President Tom Stephens says GM will continue to press forward on all technology fronts, including hybrids, alternative fuels, and plug-in electrics. "If you know the history of General Motors, it's in our DNA to be technology leaders," he says. "We have to lead the world in advanced propulsion technology: gas, diesel, hybrids, electric. I don't mean come in second. We have to be the leaders." As the baddest production engine ever offered by Detroit, the LS9 is simply one more part of the mission as Stephens sees it-reestablishing GM's engineering leadership among the world's automakers. Sorry, consumers, but you will just have to have your cake and eat it too.

Stephens says he is a little fuzzy about the precise origins of the LS9 and the ZR1, just how the scheme was hatched. But as he remembers it, "We had the Z06 done, and there was a meeting where we were asked, 'Well, what else can we do from here? How can we top this? What is the pinnacle? What could we do with a super Corvette?' At General Motors that's all the motivation you need. Working with the Corvette team, we decided what we needed in an engine for such a vehicle. And what we shot for was 100 hp per liter. And let's make sure that with this vehicle we have all the torque to go with it."

"Back in January of 2005 we made our first presentation to Tom Stephens and his staff," says Ron Meegan, assistant chief engineer. "After reviews and analysis, in May of 2005 we got the corporation to agree that yes, this is what we want to do, and in April of 2006 we got the production approval. The first job was setting the right objectives. We defined the power levels first through up-front analysis. We already determined that we needed a supercharged engine, and that for that reason we were going to use the 6.2L block rather than the 7.0L. Since 100 hp per liter was a realistic number in our estimation, that's where the original 620 figure comes from."

When Meegan refers to "up-front analysis," what he means is that the LS9 was conceived, tested, and proven as a concept before it ever made its first dyno pull. Using advanced simulation and modeling software, Gerry Clark (whose title is technical specialist, engine performance and valvetrain analysis) and his team built the engine in the computer and made sure it could hit the numbers; only then did the project proceed. "We do all our early dyno testing with engines that do not exist in metal," Clark says. "It's all bits and bytes. I was really pleased when the first beta engine on the dyno ran the number. We were right on within a couple of horsepower, bang."