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The second General Motors engine built on the Gen III platform was the LS6. The LS6 was designed to be a higher power version of its predecessor, the LS1.
Many without close knowledge might assume that the LS6 is the follower of the LS5, but the LS naming convention is not serial in terms of its introduction to production.
The standard automotive offering for the LS6 was fairly limited, and likely part of the motivation was to maintain an exclusive status. The engine was first offered in the Corvette Z06 while later being made available in the original version of the Cadillac CTS-V, the muscled up version of the Cadillac CTS.
The LS6 was first available to the public in the 2001 Corvette Z06 version, and remained available in the Corvette until being phased out in 2004. The other standard offering for the LS6, the Cadillac CTS-V, introduced the engine with its 2004 inception, but the engine remained in this model through 2005.
While not still in normal production, crate engines of this model can be found easily and this engine can likely be found in many project cars across the country.
There were several tweaks from the LS1 to the LS6, but the primary result that everyone cares about in this engine is more power. The block strength was increased enabling an increase in power, also through increased compression ratios. Also, the breathing system was optimized for improved flow, and the more air you can get into the cylinders, the more fuel you can burn, and ultimately get more power.
LS6 Performance Specs
The original introduction of the LS6 in 2001 was rated at 385 horsepower and 385 lb-ft of torque, already a significant improvement over the LS1 and quite a feat for a naturally aspirated engine at that time.
If that wasn’t enough, in 2002 the peak horsepower was bumped up to 405 at 6000 RPM and the torque was increased to 400 lb-ft at 4800 RPM. The LS6 was able to accomplish this while maintaining the same engine displacement of 346 cubic inches as the LS1.
The LS6 also carried over the bore of 3.90 inches and a stroke of 3.62 inches from the LS1, but the compression ratio was increased from 10.25:1 for the LS1 to 10.5:1 in the LS6. This bore of 3.90 inches smaller than many of the later Gen III and IV engines, and reduced the head compatibility for this engine.
Head and Block Construction
The LS6 engine is only offered with aluminum block and cylinder head. There was a modification to the casting, however, that increased the strength of the LS6 block. The pistons are constructed of hypereutectic aluminum alloy, as is common with almost all of the LS engine family.
The hypereutectic alloy simply means that the solution of aluminum and silicon is such that there is more silicon than is soluble at the operating temperatures. The primary reason for using this type of construction is to lower the coefficient of expansion of the aluminum, allowing much tighter fit to be designed between the piston and the cylinder.
The LS6 uses a conventional push rod overhead valve (OHV) valve train. The valve architecture uses 2 valves, 1 intake and 1 exhaust per cylinder.
The LS6 was a limited offering engine that truly pushed the performance of the LS1. With improved strength and breathing, along with other less noticeable changes, the power of the LS6 was 55 horsepower greater with the LS6. The extra power offered by this engine was certainly a strong selling point with power lovers that would normally be interested in the Corvette family.
Although a powerful engine, it only lasted from 2001 to 2004 in the Corvette Z06 as the need to constantly push the envelope and have the latest and greatest is especially critical in this high performance market.