More Power Is The Byword For The 2003 Chevrolet Corvette — At Least For The Top-Performing Z06 Hardtop, Which Debuted In 2001. Chevrolet’s Regular 5.7-Liter LS1 V-8 Engine Stands Pat At 350 Horsepower, But The LS6 Edition In The Z06 Coupe Has Gained 20 HP And Now Cranks Out 405 Horses. That Makes The 2003 Z06 The Quickest, Most Powerful Corvette From 2003.