We got a release from the folks at the General yesterday, and we were told we could run it at midnight-plus-one, but then we forgot about it. These things happen, you know. We mean, who gets excited about something as fait accompli as the 2009 Corvette ZR1 getting just over 620 HP? Well, if your answer is everyone, you're probably right. And why shouldn't we be excited about Zee new Really fast One from Chevy? Especially since they've now got officially certified power ratings on that beautiful Jakegasmic LS9 engine — 638 HP, nearly 103 horses per liter — and 604 lb-ft of torque, which'll let the new supercharged Corvette ZR1 break that all-important 200 MPH speed barrier. We knew there was a reason we liked this from the moment we first exploded the LS9 for all to see. Next question however is whether Wes will be back in the road test saddle in time for what we're expecting will be a summertime drive of the new ZR1 or whether it'll have to be one of us other Jalops jumping behind the wheel of the supercharged new Corvette. This may be the first time we've ever hoped someone wouldn't get better as quickly as possible. We kid. On the square. Anyway, what we do know is we've got the full press release after the jump.

CHEVROLET ANNOUCES CERTIFIED POWER RATINGS FOR THE NEW CHEVROLET CORVETTE ZR1: 638 HP FROM THE SUPERCHARGED LS9 V-8

PONTIAC, Mich. - When it was introduced at the North American International Auto Show in Detroit earlier this year, the 2009 Chevrolet Corvette ZR1's power was estimated at 100 horsepower for each of its 6.2 liters of displacement. GM Powertrain has completed SAE certification of the ZR1's supercharged LS9 V-8 and the results exceed the estimate: 638 horsepower (476 kW) and 604 lb.-ft. of torque (819 Nm).

The LS9's output is nearly 103 horses per liter, or just about 1.7 horses for each of the engine's 376 cubic inches. It is unquestionably the most powerful automotive production engine ever manufactured by General Motors and enables the Corvette ZR1 to achieve a top speed of more than 200 mph (322 km/h).

"One of the most amazing things about the Corvette ZR1 is the level of refinement that our designers and engineers have attained. Even with all that power, this car has road manners that will allow our customers to enjoy it on the streets as a daily driver, and on the track," said Chevrolet General Manager Ed Peper.

The Corvette ZR1 goes on sale this summer. Its 638-hp supercharged engine is complemented in the chassis by heavy-duty components not offered in any other model, including a six-speed manual transmission with race-hardened gears and dual-disc clutch technology that delivers exceptional clamping power and lower inertia, as well as strengthened axle components.

Fuel economy testing has not been completed, but engineers are confident the ZR1 will be the most fuel-efficient 600-plus-horsepower car on the market.

The LS9 engine is hand-built by specially trained technicians at GM's Performance Build Center in Wixom, Mich. It is a unique, small-volume engine production facility that also builds the Chevrolet Corvette Z06's LS7 engine and other high-performance GM production engines.

"Developing the LS9 involved more than simply striving for a great horsepower number. Endurance and reliability testing have shown the engine to be robust and low-maintenance, just like other engines in the small-block family," said Sam Winegarden, executive director, engine engineering for GM Powertrain. "That it is distinguished as the most powerful engine ever from General Motors is a source of immense pride among everyone involved with the LS9."

Supercharged aspiration
The key enabler of the LS9's performance is the industry's first production application of a new, positive-displacement Roots-type supercharger that has a unique four-lobe rotor design. Its design promotes quieter and more efficient performance, while the large, 2.3-liter displacement ensures adequate air volume at high rpm. Maximum boost pressure is 10.5 psi (0.72 bar). It is teamed with an integrated charge cooling system that reduces inlet air temperature for maximum performance.

"The combination of large displacement and the new, four-rotor design broadens the effective range of the supercharger, allowing the engine to make more power at lower rpm and sustain it throughout the power band," said Winegarden. "The low-end torque is tremendous and the high-rpm charge from the supercharger is simply amazing."

A raised hood provides adequate clearance for the LS9, while a polycarbonate window in the hood provides a view of the engine beneath it.

LS9 details
The LS9 features many unique design and manufacturing details that support its high-performance nature. They include:
Aluminum cylinder block with iron cylinder liners that are finish-bored and honed with a deck plate installed
Forged steel crankshaft with a nine-bolt flange
Titanium connecting rods and forged aluminum pistons
Stronger, rotocast cylinder heads with 2.16-inch (55 mm) titanium intake valves and 1.59-inch (40.4 mm) hollow-stem, sodium-filled exhaust valves
Camshaft with 0.555-inch (14.1 mm) lift for excellent idle and low-speed driving qualities
A dry-sump oiling system with 10.5-quart (9.9 liters) capacity
Integrated oil cooler and piston-cooling oil squirters
Intercooler cover visible through the hood window that features ZR1-unique blue accents and "LS9 SUPERCHARGED" embossed on the left and right sides

General Motors Corp. (NYSE: GM), the world's largest automaker, has been the annual global industry sales leader for 77 years. Founded in 1908, GM today employs about 266,000 people around the world. With global headquarters in Detroit, GM manufactures its cars and trucks in 35 countries. In 2007, nearly 9.37 million GM cars and trucks were sold globally under the following brands: Buick, Cadillac, Chevrolet, GMC, GM Daewoo, Holden, HUMMER, Opel, Pontiac, Saab, Saturn, Vauxhall and Wuling. GM's OnStar subsidiary is the industry leader in vehicle safety, security and information services. More information on GM can be found at www.gm.com.

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Specifications

LS9 6.2L SUPERCHARGED V-8
Displacement (cu in / cc):
376 / 6162
Bore & stroke (in / mm):
4.06 x 3.62 / 103.25 x 92
Block material:
cast aluminum
Cylinder head material:
A356-T6 rotocast aluminum
Valvetrain:
overhead valve, 2 valves per cylinder
Fuel delivery:
SFI (sequential fuel injection)
Compression ratio:
9.1:1
Horsepower / kW:
638 / 476 @ 6500 rpm
Torque (lb-ft / Nm):
604 / 819 @ 3800 rpm
Fuel shut-off (rpm):
6600
Recommended fuel:
premium required
Exhaust manifolds:
stainless steel
Main bearing caps:
forged steel
Crankshaft:
forged steel
Camshaft:
hollow steel; 0.555-in (14.1 mm) lift
Connecting rods:
forged titanium
Valves:
intake: titanium
exhaust: hollow steel
Valve lifters:
hydraulic roller
Supercharger:
R2300, four-lobe "Roots" type (2.3L)
Additional features:
piston oil-spray cooling; direct-mount ignition coils; 11-rib accessory drive

Send an email to Ray Wert, the author of this post, at ray@jalopnik.com.