Corvette LS Engines - Tech

Over the last dozen years, this LS engine series has gotten rather lengthy and even a little confusing. As we suspected on that morning in New Jersey, this engine was not designed just for the Corvette. Rather, it was going to find its way into a huge variety of engine compartments.

The Generation III, or LS, small-blocks replaced the LT family in 1997. They shared the same basic displacement and bore spacing (4.4 inches) as the earlier engines, but almost everything else changed.

If anything, the LS engine looked a whole lot like the Cadillac Northstar. A few GM engineers privately explained to me that the Northstar had really been a test for the new LS1. There was no way GM could justify a stand-alone engine for the Cadillac, but if it was a stalking horse for the LS1, then it was just fine. The Northstar sold in such small quantities that a screw-up wouldn't be the end of the world.

The new LS1 had a 3.9-inch bore and a 3.62-inch stroke. The idea was that this particular combination would provide significant low-end torque. Remember, it was being compared to the old LT1 engine. Performance had to be at least as good as the LT1.

This new engine also introduced coil-on-plug ignition to the small-block V-8. Finally, the Corvette could get rid of the Opti-Spark system. The cylinder firing order was changed to 1-8-7-2-6-5-4-3, so that the LS series now corresponded to the firing order of other modern V-8 engines.

The traditional five-bolt pentagonal cylinder head bolt pattern was replaced with a square four-bolt design. As the performance of this engine increased this would be a problem, but as long as you kept the power down to a reasonable level, everything was fine. Corvette Racing now runs a five-bolt cylinder head. Need to know anything else here?

The LS1 block is very different from pre-'97 small-block engine designs. Most of the internal parts, like the crank mains, front and rear covers, and oil pan, are designed to "find their own home," which simplified the machining process and eliminated the need for dowels in many locations. Good examples of this are the crankshaft main caps. These main caps swedge between the lower skirt walls of the cylinder block. GM engineers call this snap-fit cross-bolting. Cross-bolting refers to how each one is held in place with four vertical and two horizontal bolts.

The drumbeat for more Corvette power began almost as soon as the C5 Corvette was on the showroom floor. I can remember Dave Hill, the Corvette chief engineer, being besieged with questions about when "real" Corvette power would make an appearance. Being the good GM soldier that he was, Dave never hinted that the LS6 was just around the corner. But in 2001, we got LS6 power. This first step, which lasted only one year, delivered 346 horsepower and 385 lb-ft of torque with the six-speed transmission, and 360 lb-ft of torque with automatic transmissions.

When the '02 Z06 was introduced it got even better. Horsepower went to 405 and torque was increased to 400 lb-ft. Now people were happy-at least for about 10 minutes. Then the appeals for more power began anew.

Generation IV
In 2005, the Generation IV superseded the Generation III engine family. This marked the introduction of the LS2 engine into the Corvette. It was time to step up the displacement. This new generation of engines included provisions for displacement up to 7.0 liters (the magic 427 cubic inch number that Corvette owners all love and cherish) and power output to 638 hp. It was time to get serious.