Inside the LS3: An illustrated look at the engine that powers the 2008 Chevrolet Corvette
Source: Motor Trend Magazine
July 24, 2007
The immortal Chevy small block has been extensively revised. Again. In this latest LS3 iteration, a 0.06-inch increase in bore bumps displacement from the LS2's 6.0 to 6.2 liters. But it took way more than a little cylinder-bore honing to wring another 30-36 horsepower out of this venerable engine. Improvements in breathing, lowering the reciprocating masses, and strengthening the block all played important roles in this redesign.
Better breathing starts in the intake manifold, which uses a new lost-core casting technique and eliminates "cross talk" between cylinders (acoustic waves bouncing off closing intake valves can impede airflow in adjacent cylinders). This change alone is credited with five horsepower. Note also the new acoustic "helmet" that sits atop the intake manifold. It quells some higher frequency sounds that contributed a slightly agricultural thrash to the LS2. A resonator is also used to help knock out unwanted induction noise frequencies without disturbing the ones we love.
Once the air leaves this new manifold it flows through the head in a wider, smoother, squarer sectioned runner to the valve. Redesigning the intake runners in the cylinder heads from a tall rectangular section to the wider squarer design required moving the pushrod over 6mm. This was done by using new rocker arms in which the valve is offset from the pushrod.
The intake valves themselves are way bigger-55mm versus the LS2's 50.8mm. To offset the added mass of the larger valve, the stems are hollow. This helps preserve the lofty 6500 rpm redline. Valve lift is also increased, from 13.25mm to 14.00mm and the overlap is reduced. Overall intake airflow is improved by 17 percent. With added airflow comes added fuel flow-the Z06's high-flow injectors are now fitted.
It's difficult to detect, but the top rings on the LS3's pistons are tilted slightly upward. The oil-control rings are also lighter weight, and new holes drain oil away from these rings. A higher grade of bolt is used on the piston rods, and they're better positioned.
The result of these changes and more is in increase in peak output rise from 400 hp/400 lb-ft to 430/424 or 436/428 with the low-restriction dual-mode exhaust system. Fuel economy is expected to remain unchanged (though changes in the way EPA numbers are calculated will make it seem as though economy has worsened). There is still no guzzler tax, the car runs on regular fuel, and emissions are even improved-by 40 percent in NOx and 12 percent in hydrocarbons. The LS3 is even more efficient to manufacture. It's a true win-win-win situation.