11) LT5 350/375-405HP
(3.90 X 3.66)
Back in the late ’80s, the Corvette was the hot ticket with its 240-250-horse Tuned Port injected, pushrod small-block. It topped out at over 150 mph and ran 13s in the quarter-mile, but then rumors started flowing about a Corvette supercar (known to insiders as the King of the Hill). The rumors turned out to be true. In development with newly-acquired Lotus, Chevy developed the ZR-1, a 180-mph supercar that could blow away the Ferraris of the day. It was powered by the all-new and all-alloy LT5 V-8, which made 375 horsepower thanks to its dual-overhead cam, 32-valve, 350-cid engine. The ZR1 option added a staggering $27,016 to the price of a $31,979 base Vette, but in the supercar realm it was a bargain. Quarter-mile times were in the 12.8-13.0 range at 110 mph. While its 375 horsepower in ’90 doesn’t sound like much at a time when the base Corvette makes 430 horsepower, it offered a 50-percent increase in power over the base Vette in ’90. The LT5’s crowning achievement was setting a 24-hour endurance speed average of 175.8 mph—including fuel stops. King of the Hill, indeed!
12) LS1 346/345HP
(3.898 X 3.62)
GM had introduced the Gen II small-block, the LT1, in the ’92 Corvette, so it was a bit of a shock when the 1997 Corvette was introduced with a totally new engine. The LS1 shared the traditional small-block’s 4.4-inch bore spacing, but precious little else. The all-aluminum block had a deep-skirt design, and not only did it feature four-bolt main caps, but also two cross-bolts for additional durability. The cylinder heads were also aluminum and in a radical departure did not have the Siamese center intake ports small-block Chevys had been know for since ’55. The benefit here is vastly improved port geometry and race-like cylinder head flow. The LS1 heads flow 245 cfm from the factory. The cam bores were larger and located higher in the block. Fully assembled, it weighs 100 pounds less than a Gen I SBC. While it was replaced a few years later by the even better Gen IV LS2 small-block, the LS1 started a performance revolution in 1997, one which is still growing in 2011.
13) LS6 346/385-405HP
(3.898 X 3.62)
While it shared the LS1’s bore and stroke, the LS6 engine was a different animal from the block up and, installed only in the new- for-2002 Corvette ZO6, picked up the supercar mantle missing in the Corvette lineup since the discontinuation of the ZR-1 in 1995—at a fraction of that car’s price. It had a new intake and exhaust manifolds, a higher-lift cam, and high-flowing cylinder heads to produce 385 horsepower. In the lightweight ZO6, this was enough to propel them to 11-second quarter-mile times in factory trim, far eclipsing the performance of the ZR-1 in every way except top speed (which was approximately 171 mph). A year later, the LS6 got a host of upgrades, including a freer flowing exhaust, a higher-lift cam, lighter (hollow) intake and (liquid-filled) exhaust valves to bring the power total to 405 (though reports are this was intentionally underrated by the factory). The ZO6 engines of 2001-2004 had a completely different feel than the standard LS1s and even today’s ZO6, more like that of a tamed race engine than a high-output street motor.
14) LS7 427.5/505HP
(4.125 X 4.00)
The most powerful naturally-aspirated engine in Chevy’s history comes in an all-aluminum package and hosts a number of innovations— including dry-sump oiling in a production vehicle and press-fit iron cylinder liners instead of cast-iron sleeves. A forged-steel crank, titanium rods, hypereutectic pistons, and doweled steel main caps make up the bulk of the bottom end. The cam has nearly 0.600 inch of lift, with 211/230 @ 0.050 duration. The 12-degree heads are CNC-ported at the factory and use 2.20/1.61- inch valves. The engine revs freely to 7,000rpm, and in the lightweight package it comes in (2006-present Corvette ZO6) can run mid-to-low 11-second quarter-mile times off the showroom floor, with a top speed of 198 mph. It’s a Hall of Famer in any book.
15) LS9 376/638HP
(4.065 X 3.622)
For the ultimate small-block performer, Chevy added a Roots-style supercharger to a 6.2-liter engine to create the LS9. The block is cast from 319-T7 aluminum for added strength and features larger bulkheads than the standard LS7 block. Inside are titanium rods, a steel crank, and forged 9.1:1 pistons. Instead of using the expensive and more exotic ZO6 heads, the ZR1 uses casts that are similar to that of the LS3 but made from A-356-T6 aluminum. Up top, a 2.3-liter Eaton supercharger puts 10.5 psi of boost through a dual-core intercooler. It makes enough grunt to propel the ZR1 to 205 mph. If you have the means, GM Performance Parts will sell you an LS9 crate engine for about $22,000.