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GM LS engine

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GM's LS7 engine powering the Chevrolet Corvette C6
The LS Generation III and Generation IV, the latest evolution of General Motors' line of small-block V8 engines. The LS series was a clean sheet design, drawing on the heritage of the classic small-block, but is all-aluminum and has 6-bolt main bearing caps. The LS engine has been the sole powerplant of the Chevrolet Corvette since 1997, and has seen use in a wide variety of other General Motors vehicles ranging from pony cars to full size trucks.

Generation III

The Generation III small-blocks replaced the LT family in 1997. These shared the same rough displacement and bore spacing (4.4") as their cast iron predecessors but almost everything else was changed. The bore was reduced to 3.9 in and the stroke longer at 3.62 in for greater low end torque. The engine blocks were cast in aluminum for car applications, and iron for most truck applications (notable exceptions include the Chevrolet TrailBlazer). The engine also introduced coil-on-plug ignition to the small-block V8. The traditional five-bolt pentagonal cylinder head pattern was replaced with a square four-bolt design, and the pistons are of the flat-topped variety. The cylinder firing order was changed to 1-8-7-2-6-5-4-3, so that the LS series now corresponds to the firing order of other modern V8 engines.


Engine List

Generation IV

In 2004, the Generation III was superseded by the Generation IV. These big-bore engines are some of the largest small-blocks yet, and were quickly phased in to replace the previous generation. Displacement ranges up to 7.0 L and output to 505 hp (373 kW). Building upon the Generation III design, Generation IV was designed with displacement on demand in mind, a technology that allows one bank of cylinders to be deactivated. It can also accommodate variable valve timing. A 3-valve per cylinder design was originally slated for the LS7, which would have been a first for a pushrod engine; but the idea was shelved owing to design complexities and when the same two-valve configuration as the other Generation III and IV engines proved to be sufficient to meet the goals for the LS7.

Engine List

Photos

Unique Attributes

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Criticisms

In the early production run of the LS-series engine, some engines encountered abnormal amounts of 'piston slap' - a problem caused by too much clearance between the cylinder bore and the piston. However, the scope of the problem appears to be fairly limited as no recall has been issued by General Motors, and the majority of owners of these engines do not report this issue. Additionally, it appears that this issue is confined only to a small number of the engines produced between 1997 and 2002.

'Piston Slap' should not be confused with a light ticking sound often produced by some of these engines that often goes away when the engine warms up. This is usually the sound of the lifters ticking. 'Piston Slap' sometimes sounds more like a nock or the sound of a diesel engine running. The noise of 'Piston Slap' often is louder when listening for it below the oil pan.


Worldwide

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Design quirks and oddities

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Awards

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See Also

Template:Chevrolet

Template:GM LS Engine

External Links