The Complete History of GM's LS Small

Jul 09, 2023

Since their introduction in the late 1990's, the LS-series engines have become a cornerstone of the Chevrolet Corvette. While variants of Chevrolet's small-block engine have carried the LS designation since the 1960's, GM introduced a series of LS engines beginning in 1997 that became the sole, dominant powerplant for the fifth (C5) and sixth (C6) generation Corvettes. Today, these engines are recognized globally for their durability, longevity and reliability. They’re so popular among automotive enthusiasts (including non-GM car builders and owners) that they’ve become the "go-to" swap for many high-performance vehicles – from track-purposed Ford Mustangs and Mazda Miatas to off-road purposed vehicles like the Jeep Wrangler. The LS engine platform has garnered such a following that each year a pair of "LS Fest" events are hosted by the Holley company – one in Las Vegas and one in Bowling Green, Kentucky.

What follows below is an overview of each of the Gen III and Gen IV engines that Chevrolet introduced in the Corvette from 1997 to 2013. Many of these engines were also used in other applications – including a significant number of other GM products including the Chevy Camaro, the Pontiac GTO and so on. They were also the primary powerplant used by Holden Special Vehicles (HSV). Holden, formerly known as General Motors-Holden, is an Australian carmaker and former automobile manufacturer. HSV is the officially designated performance vehicle division of Holden. Headquartered in Port Melbourne, Victoria, a suburb of Melbourne, Australia, the company's Special Vehicle division modified a number of GM and Holden vehicles for sale both in Australia and abroad.

Chevrolet began utilizing the LS1 engine in the Corvette when they introduced the C5 in 1997. When first introduced, the LS1 was rated at 345 horsepower (257W) at 5,600 rpm and 350 lb./ft. of torque (475 Nm) at 4,400 rpm. The same powerplant was utilized (virtually unchanged) thru 2000. In 2001, improvements were made to the LS1's intake and exhaust manifolds. The results of these changes was a small bump in horsepower in torque – 345 to 350 horsepower and 350 lb./ft. to 365 lb./ft. of torque, respectively.

The LS1 engine was used as the sole powerplant for the Chevy Corvette coupe and convertible from 1997 thru 2004. In addition to the Corvette, the LS1 was also utilized in both the Chevy Camaro and the Pontiac Trans Am from 1998 thru 2002. The reported output from the Camaro and Trans Am was documented by GM at just 325 horsepower, though this number was generally considered conservative and varied some based on factory options (such as in the SS (Chevrolet) and the WS6 (Pontiac) models). Both of these variants featured a ram-air injection system that allegedly produced significantly higher horsepower ratings than those published by GM when these pony cars were new.

In Australia, conti nuous modifications were made to the LS1 engine throughout its lifetime, reaching 380 horsepower and 365 lb./ft. of torque in the Holden Special Vehicles YII series. A Callaway modified version of the LS1 dubbed the "C4B" was also fitted to HSV GTS models. This engine was capable of producing 400 horsepower (298 kW) and 405 lb./ft. (549 N⋅m) of torque.

In 2001, Chevrolet introduced their fifth-generation Z06 Corvette Coupe to the world. At the core of the track-ready Z06 was a higher-output version of GM's LS1 engine designated the LS6.

The initial 2001 LS6 engine produced 385 horsepower (287 kW) and 385 lb./ft (522 Nm) of torque, though the engine was modified for the 2002 model year to an even healthier 405 horsepower (302 kW) and 400 lb./ft. (542 Nm) of torque. This latter engine would continue to power the C5 Z06 thru the end of the 2004 model year.

The LS6 engine shared the same basic block architecture as the LS1 engine, though modifications were made to improve the engine's ability to breathe, to operate under higher compression (10.5:1) and to improve overall structural rigidity. Windows were cast into the block between the engine cylinders, higher-flow intake manifolds with MAF (Mass Air Flow) sensors were introduced, a camshaft with higher lift and more duration was installed. More than that, the engine featured sodium-filled valves, a revised oiling system that operated better under high lateral acceleration, improved main web strength and bay-to-bay breathing.

It should be noted that the LS6 intake manifolds were utilized on all 2001+ LS1/LS6 engines. The casting number for these manifolds – GM part/casting number 12561168 – can be found on the top rear edge of the block.

In addition to the 2001–2004 Corvette Z06, the LS6 engine was also installed in the Cadillac CTS V-series. So configured, the Cadillac variant of the engine was rated at 400 horsepower. The V-Series Cadillac continued to use the LS6 thru the 2005 model year before it was replaced by the LS2 in 2006. In 2007, the SSC Ultimate Aero TT also utilized the LS6 powerplant for a single model year.

For reference, the LS6 designation was also used by General Motors on a 454 CID Chevrolet Big-Block engine produced in the early-to-mid 1970s, as well as an iteration of the GM Iron Duke engine built in the late 1970s. While these engines are not specifically referenced in this article, we did want to acknowledge the use of the LS6 engine designation prior to the powerplant referenced above.

The LS2 engine was introduced by GM in 2005 as the new base engine for the C6 Corvette as well as the standard powerplant for the 2005-2006 Pontiac GTO.

When first introduced, GM stated that the LS2 was built on the new Gen IV small-block architecture. The primary difference between it and the previous Gen III (LS1) engines was that the LS2 used a new block casting. In reality, it was actually a revised version of the Gen III's cylinder case. In fact, the blocks were so similar that many of the Gen III parts carried over from the LS1 to the LS2, including the LS6-style cylinder heads used on the LS2. Here are the major differences between the Gen III and Gen IV blocks:

The remainder of the block's features, from the six-bolt main bearing cap design (four vertical bolts and two cross-bolts) and deep-skirted case remain unchanged.

The LS2 produced 400 horsepower (298 kW) at 6,000 rpm and 400 lb./ft. (542 Nm) of torque at 4,400 rpm. At 6.0 liters, the LS2 had a slightly larger displacement at 364.1 cubic inches (5,967 cc) than the standard 5.7 liter engine (350 cubic inch, 5735 cc) most synonymous with Chevrolet. The engine was similar to the high-performance LS6 introduced/utilized in the fifth-generation Z06 Corvette, but with improved torque throughout the entire power-band range. The LS2 utilized the "243" casting heads previously used on the LS6 (less the sodium-filled valves) and a smaller camshaft. The compression ratio of the LS2 engine was increased to 10.9:1 over the Ls6's 10.5:1.

Australian LS2 engines were modified to produce 412 horsepower (307 kW) and 412 lb./ft. of torque. These engines were introduced in the E-series Holden Special Vevhicles (HSV).

For reference, the LS6 designation was also used by General Motors on the 1973-1974 Super Duty 455 cubic inch (7.5 liter) Pontiac V8 engine as well as the 1985 Oldsmobile Diesel V6 engine. While these engines are not specifically referenced in this article, we did want to acknowledge the use of the LS2 engine designation prior to the powerplant referenced above.

Chevrolet introduced a new Z06 Corvette as a 2006 model in the third quarter of 2005. The Z06 was equipped with the largest-displacement small-block engine ever produced to that point – the all-new LS7 engine.

Each LS7 engine was hand-built at the General Motors Performance Build Center in Wixom, Michigan. Most of these engines were later installed in the Z06 Corvette, although some were sold to individuals by GM as a crate engine.

The LS7 was a 427.8 cubic inch (7,011 cc) 7.0 liter engine that was based on Chevrolet's Gen IV engine architecture. The engine was rated with a peak output of 505 horsepower (377 kW) at 6,300 rpm and 470 lb./ft. of torque at 4,800 rpm. The engine featured a 7,000 rpm redline. Although the LS7 was derived from the earlier LS2 engine, the block was changed and included sleeved iron cylinders mounted within an aluminum block. Each cylinder had a larger bore of 4.125 inches (104.8 mm) and a longer stroke of 4 inches (101.6 mm). The engine featured a forged-steel crankshaft and main bearings, forged titanium connecting rods and pistons comprised of a hypereutectic alloy–that is, a metallic alloy which has a composition beyond the eutectic point (the temperature at which a particular eutectic mixture freezes or melts.) The engine utilized the same two-valve arrangement as that of the LS2, though the titanium intake valves by Del West were increased in size to 2.2 inches (56 m) and increased, sodium-filled exhast valves at 1.61 inches (41 mm).

It has been reported that when General Motors was performing reliability testing on the LS7 engine, it was repeatedly tested to be 8000 rpm capable. Despite this claim, GM did not document the power output at that rpm level due to the constraints of the camshaft's hydraulic lifters and the intake manifold's ability to flow the necessary air at that engine speed.

Holden Special Vehicles (HSV) further refined the LS7 engine over a period of several years before introducing the engine in their special edition W427 coupe (similar to the Pontiac G9 from that same era.) The HSV-tuned LS6 engine produced 503 horsepower (375kW) at 6,500rpm and 472 lb./ft (640Nm) of torque. The W427 was first unveiled at the Melbourne International Motor Show on February 29, 2008 and went on sale in August.

The LS3 was introduced by Chevrolet as the standard powerplant for the 2008 (and later) Corvette. This new engine produced 430 horsepower (321 kW) at 5,900 rpm and 424 lb./ft (575 Nm) of torque (these numbers are SAE certified), both of which were appreciable gains over the outgoing LS2.

The LS3 block was an updated version of the LS2 casting though it featured a larger bore of 4.065 inches (103.25 mm). This resulted in a displacement of 376.0 cubic inches (6,162 cc) or 6.2 liters. The LS3 featured higher flowing cylinder heads (originally sourced from the L92 engine), a more aggressive camshaft with 0.551 inch (14 mm) lift, a 10.7:1 compression ratio, a revised valve-train with 0.236 inch (6 mm) offset intake rocker arms, a high-flow manifold and 47 lb (21 kg)/hr fuel injectors from the LS7 engine.

The LS3's cylinder heads use 2.165 inch (55 mm) intake valves and 1.59 inch (40 mm) exhaust valves. Improved manufacturing efficiencies made these heads cheaper to manufacture than the outgoing LS6 heads. However the large valves (which utilized hollow-stem technology) used in these heads limited the engine's maximum rpm to 6,600.

Additionally, a dual-mode exhaust package was offered on C6 Corvettes. This dual-mode exhaust utilized vacuum-actuated outlet valves that controlled engine noise during low-load operation, but would open for maximum performance during high-load operation. This system is similar to the C6 z06, but used a 2.5 inch (64 mm) diameter exhaust. When engaged, this option actually increased the LS3's horsepower to 436 hp (325 kW) and 428 lb./ft. (580 Nm) of torque.

In April 2008, Australian Holden Special Vehicles adopted the LS3 as its standard V8 throughout its entire range of vehicles. The LS3 as modified for use in the HSV E Series models, resulting in an output of 425 horsepower (317 kW). The LS3 engine in the E Series II GTS (released September 2009) was upgraded to produce 436 horsepower (325 kW).

In September 2015, Holden introduced the LS3 in all V8 models of the VF II Commodore and WN II Caprice-V.

For reference, the LS3 designation can also refer to a 402 cu in (6.6 L) Chevrolet Big-Block engine of the 1970's.

The Gen IV LS9 engine was introduced in 2009 as the powerplant for the sixth-generation Corvette ZR1. The LS9's power output was measured and ASE Certified at 638 horsepower (476 kW) at 6,500 rpm and 604 lb./ft. (819 Nm) of torque at 3,800 rpm.

The LS9 was a supercharged 6.2 liter (6,162 cc) engine that was based on the LS3, and not the LS7 (as some assumed it would be given that the LS7 was the standard powerplant in the other performance variant of the C6 generation – the Z06 Corvette.) The LS3 served as the base block because its thicker cylinder walls were better equipped to handle the higher cylinder pressures created by the LS9's supercharger. The engine block used with the LS9 was cast from 319-T7 aluminum and fitted with cast-iron cylinder liners. It was strengthened 20 percent (compared to prior generations of this engine) by optimizing the size of the bulkhead "windows" to take advantage of material thickness in the bulkhead. The enlarged bulkhead windows also improve bay-to-bay breathing by managing airflow inside the engine more efficiently, thereby decreasing pumping loss, or reducing resistance to the pistons’ downward movement. The engine's cylinder dimensions had a bore of 4.065 inches (103.25 mm) and a stroke of 3.622 inches (92 mm). The engine was paired with an Eaton four-lobe Roots-type supercharger and had a compression ratio of 9.1:1.

The LS9's pistons were constructed of premium forged aluminum components. This construction resulted in a high-performance combination of low mass, high strength and durability. The LS9's pistons were considerably lighter than conventional aluminum pistons, which translated into less reciprocating mass inside the engine. The LS9 also incorporated oil-spray piston cooling. Eight oil-squirting jets in the engine block sprayed the underside of each piston and the surrounding cylinder wall with an extra layer of cooling, friction-reducing oil. The oil spray reduced piston temperature, which promoted extreme output and long-term durability.

To ensure proper fuel delivery under all conditions, the LS9 featured a dual-pressure fuel delivery system. It delivered about 36 psi (250 kPa) when the engine was at idle or operating at low speeds. During sudden, hard acceleration, the electronic throttle management system could immediately increase fuel pressure to 87 psi (600 kPa) for sustained high-speed operation or wide-open throttle. The dual-pressure system reacted according to throttle application and presented several advantages. It limits the amount of energy used by the fuel pump at low speeds for maximum efficiency, and it reduced operational noise.

The LS9 also employed a center-feed fuel rail that delivered gasoline to the center of the injector rail and each bank. This helped reduce fuel pressure variation among the injectors as well as noise (which had been a complaint of some consumers on earlier iterations of the LS engine.)

Introduction of state-of-the-art supercharging technology was the cornerstone of the LS9's remarkable engine performance. The supercharger utilized an air pump driven by the engine's crankshaft. It forced more air into the engine's combustion chambers than the engine could otherwise draw-in on its own. The increased volume of oxygen allowed the engine to efficiently process more fuel and thus generate more power. Additionally, an advanced intercooling system increased the LS9's performance and extended its supercharger's benefits. The engine's charge cooler was integrated in the supercharger case just above the rotors with two air-to-liquid cooling "bricks" that substantially lowered the temperature of air used in the combustion process.

For reference, GM previously used the LS9 engine designation for powerplants used in 1969 and later Chevrolet trucks (both 2WD and 4WD) including Blazers, Jimmys, Suburbans, as well as car carriers. The original LS9 was a 350 cu in (5.7 liter) V8, developing 160 hp (119 kW) and 245 lb⋅ft (332 Nm) of torque.

The LS4 engine was a 5.3 litre, 325.1 cubic inch (5,327 cc) engine that was adapted for transverse, front-wheel drive applications. It featured an aluminum block instead of iron and used the same cylinder head castings as the Generation III LS6 engine. The bell housing bolt pattern is different than those used on rear-wheel drive blocks. Engine output of the LS4 was rated at 303 horsepower (226 kW), with one exception being an output of 300 hp on the LaCrosse Super and 323 lb⋅ft (438 N⋅m).

According to General Motors, "The crankshaft is shortened 13–3 mm (0.51–0.12 in) at the flywheel end and 10 mm (0.39 in) at the accessory drive end – to reduce the length of the engine compared to the 6.0 L. All accessories are driven by a single serpentine belt to save space. The water pump is mounted remotely with an elongated pump manifold that connects it to the coolant passages. Revised oil pan baffles, or windage trays, are incorporated into the LS4 to ensure that the oil sump stays loaded during high-g cornering."

Applications:

The LSA was a supercharged 6.2 liter engine that was very similar to the LS9 in most respects. It was first introduced in the 2009 Cadillac CTS-V. The LSA was SAE certified at 556 horsepower (415 kW) at 6,100 rpm and 551 lb./ft. (747 Nm) of torque at 3,800 rpm. General Motors called it "the most powerful (engine) ever offered in Cadillac's nearly 106-year history." While the LSA and LS9 engines are virtually the same, the LSA did incorporate a smaller 1.9 liter supercharger, a slightly lower 9.0:1 compression ratio, a single-unit heat exchanger and cast pistons.

A 580 horsepower version of the LSA engine was used in the 2012 Camaro ZL1.

The LS7.R engine was a racing variation of the LS7 engine that was used in the highly successful C6.R Corvette American Le Mans Series race car. It was crowned as Global Motorsport Engine of the Year by a jury of 50 race engine engineers at the 2006 Professional Motorsport World Expo in Cologne, Germany.

GM Performance Parts introduced the LSX engine at the 2006 SEMA show. It was an all-new cast-iron racing block based on the LS7 engine. The engine was developed/designed with help from drag racing legend Warren Johnson.

The engine offers displacements ranging from 364 cubic inches to 511 cubic inches (6.0 liter to 8.4 liter) and is capable of producing up to 2,500 horsepower (1,864 kW). The block incorporates two extra rows of head-bolt holes per bank for increased clamping capacity. The six bolt steel main caps are the same as those used on the LS7 engine.

For reference, LSx is also used to denote any LS engine

Chevrolet Performance LSX376 crate engines are updated versions of the LSX crate engine family designed to support up to 1,000 hp (746 kW). All models used Chevrolet Performance an LSX Bowtie block.

Noonan Race Engineering developed two billet aluminium blocks based on the LS engine. Bores sizes up to 4.185 inches and strokes up to 4.5 inches are available, making it possible for a 495 cubic inch displacement. The billet construction provided added block integrity suited to high horsepower applications. The block design incorporated turbocharger pressure feed lines in the front of the valley and oil dump ports in the side of the block to return oil to the sump. In addition to the solid block, a water-jacketed version was also designed to provide better cooling options for street or endurance applications.

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