Chevrolet Corvette LS6 Small Block Engine - The Ruthless Pursuit Of Power

Hib Halverson Mar 1, 2001 0 Comment(s)
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Drive it like ya stole it, and the LS6 engine in the new Corvette Z06 kicks butt, big-time. Shift an LS6 at 6,500 rpm, just 100 rpm shy of its rev limiter. While the motor peaks at six grand, its power curve from there to the 6,600-rpm fuel cut-off is nearly flat. Better yet, it out-powers the '97-00 LS1, not just at the top end, but everywhere off idle.

This new member of the Gen III small-block engine family presents us with a chance to quantify the rate at which technology marches by comparing it to the LT5, introduced more than a dozen years ago.

The LT5 was the first American production V-8 to pass the one SAE net horsepower-per-cubic-inch mark. This all-aluminum, four-cam, 32-valve, 350-cubic-inch V-8 was in all Corvette ZR-1s and is responsible for the performance that made those cars legends.

For a dozen years, LT5 reigned as the most powerful production engine in any GM car since 1969. It kept the ZR1 King-of-the-Hill Corvette until the Z06 debuted this fall. When it was introduced in the summer of 1988, the LT5 generated 375 SAE net hp at 6,000 rpm and 370 ft-lbs of torque at 4,800 rpm. That kind of performance was cutting-edge...for its day.

LT5 Was Then. LS6 Is Now.
This new Gen III puts out 385 hp at 6,000 rpm and 385 ft-lbs of torque at 4,800 rpm. A dozen years of engine technology advancement gets us 10 horsepower and 15 ft-lbs of torque with identical peaks. If that doesn't seem like much, consider that this improvement comes from an engine with slightly less displacement, smaller physical size, only one cam, only two-valves-per-cylinder, pushrod valve gear, less weight and better fuel mileage.

Development History
GM's Generation-Three small-block engine family debuted in the 1997 Corvette as the LS1, a 346-cubic-inch, 345hp V-8. The following year, LS1 was in the F-car in a slightly different iteration, putting out either 305 hp or with optional cold air induction and low-restriction exhaust, 320hp. The LS1 was a home run right out of the box. The C5 version made one SAE and the F-car version gave the '98 Camaro performance unmatched by anything but the Vette and the Viper.

John Juriga, Assistant Chief Engineer for Gen III Passenger Car Engines at GM's Powertrain Division has been on the Gen III program since its beginning in 1992. He describes GMPT's work on those engines as the "ruthless pursuit of power." Clearly, that philosophy drove Juriga and his team of engineers as they began work on the LS6.

As Juriga's staff of engineers began full-scale development, the first major challenge was the camshaft and cylinder head package. Both pieces were significant evolutions from the LS1 parts and the work took about a year during 1997 and 1998. The other major task was a redesign of the bare block to improve its "bay-to-bay" breathing and its strength. That took place in mid-to-late 1998.

The final major challenge was a sort of "surprise" late in the program. Once prototype engines were available for installation in vehicles, race track testing demonstrated oil control and consumption problems in certain extreme duty situations. The problem, discovered in the fall of 1998, took about nine months to solve. The LS6's final development and validation was during mid-to-late 1999. Pilot engines were built in the first quarter this year and the first production units last spring.


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