Just as the original Ed Cole-design Chevrolet small-block V-8 launched an era of American performance upon its introduction in the mid-Fifties, so did the LS-series third-generation small-block Chevrolet V-8 when it launched a quarter-century ago. And just as the original SBC spawned dozens of variants over its decades-long lifespan, so did the LS – enough to bewilder all but the most dedicated of enginespotters without a comprehensive reference guide to the engine family’s various displacements, codes, and ratings. So let’s dive into it
What Sets The LS V-8 Apart
Every history of the LS calls it a clean-sheet design – that is, a design that carries nothing over from its predecessor, the Generation II LT-1. Indeed, engineers Tom Stephens and Ed Koerner retained only two parts from the LT-1 when designing the LS series: the rod bearings and the lifters. It’s a thoroughly modernized small-block, with deep side skirts, cross-bolted six-bolt main bearing caps, no provision for a distributor, no coolant passages in the composite intake manifold, cathedral-port heads, and perhaps most important, all-aluminum construction.
Yet, it’s no cutting-edge engine. Even at its introduction, critics derided its overhead-valve design – complete with the single camshaft located in the block, just two valves per cylinder, and pushrods and rocker arms in between – as antiquated. Overhead-camshaft and dual-overhead-camshaft designs had long become the standard for performance engines, after all.
As Will Handzel related in his book, How to Build High-Performance Chevy LS1/LS6 V-8s, GM engineers did have the option to continue development of the Lotus-derived LT5 dual overhead-camshaft derivative of the Generation II small-block. However, consensus at the time – and Koerner’s long and successful background in NHRA drag racing – led them to choose the pushrod design for its simplicity, its dependability, its inexpensive construction, and its compactness. Those attributes not only set the new LS engine apart from its competition, they also (in conjunction with the standard SBC bell housing pattern) led to its widespread adoption by hot-rodders in the ensuing years.
Despite those criticisms of the LS engine’s design, it has proven adaptable to use in high-performance cars (developing as much as 638 hp from the factory), front-wheel-drive cars, police cars, trucks, and SUVs. With a mid-2000s refresh – which GM dubbed Generation IV – the LS was also able to incorporate more advanced technologies such as cylinder shutdown (in GM’s nomenclature, either Displacement on Demand or Active Fuel Management) and variable valve timing and operate as a flex-fuel engine or even in mild hybrid applications.
The LS story starts with the 1997 model year C5 Corvette, in which the LS1 debuted. Like the outgoing small-block (which remained in production through 2003 in full-size vans and which GM still builds for aftermarket sales), the LS1 displaced 5.7 liters, though a smaller bore and longer stroke meant the engine now displaced 345.7 cubic inches. In the one-horsepower-per-cubic-inch tradition, it surpassed both the previous generation’s LT1 and LT4 with 345 horsepower.
As the standard-bearer for the Generation III small-block family, the LS1 provided power for the entire C5 Corvette run, made its way under the hood of the Camaro and Pontiac Firebird from 1998 through 2002, and came back for a curtain call in the 2004 Pontiac GTO. It also provided the basis for the hairier LS6.
Another 5.7-liter V-8, the LS6 came along in the 2001 Corvette Z06, boasting 385 horsepower and 385 pound-feet of torque. A year later, GM cranked that up to 405 horsepower and 400 pound-feet. The added power in the LS6 largely came from old-fashioned hot-rodding know-how – a higher compression ratio, more camshaft duration and lift, freer-flowing D-shaped exhaust port heads (stamped 243 next to the rocker cover, replacing the 241 oval-shaped exhaust port heads on the LS1) and a higher-flow mass-airflow sensor – though the LS6 also benefited from sodium-filled valves and engine block and oil system improvements. After wrapping up the C5 run, the LS6 went on to power the 2004-2005 Cadillac CTS-V.
Just as the C5 Corvette ushered in a new engine, so did the C6 with the LS2 – the first of the Generation IV small-blocks – in 2005. For the LS2, GM enlarged the engine to the 6.0-liter displacement previously used by the Generation III LS truck engines (see below), bumped the compression ratio to 10.9:1, and added the LS6’s 243 heads (albeit without the sodium-filled valves) to crank output to 400 horsepower and 400 pound-feet. Compared to the LS1 and LS6, the LS2 powered a much wider variety of vehicles: It remained in the Corvette through 2007, it finished out the Pontiac GTO’s run in 2005 and 2006, it went under the hood of the 2006-2007 CTS-V, and it served in the 2005-2006 SSR, the 2006-2009 TrailBlazer SS, and the 2008-2009 Saab 9-7x Aero.