BY DON SHERMAN
On Time Delivery
Considering the bullets Corvette engineers sweat over ounces of mass, the 22-pound weight gain necessary to upgrade the Z06’s LS7 engine to full dry-sump lubrication must have caused palpitations. “The conventional wet-sump approach used successfully with the LS2 V8 could not meet the LS7 performance targets,” says design engineer Dan Hommes.
Dry-sump lubrication is de rigueur in racing, at least whenever the rules allow. Evacuating the oil from beneath the crankcase accomplishes two ends — a lower center of gravity with the engine positioned closer to the pavement and better overall dependability. While dropping the Z06’s engine was not practical in this instance, the potential lubrication benefits alone were worth it.
Hommes explains, “The Z06 easily achieves over 1g in cornering and braking performance. That’s equivalent to tilting the engine at a 45-degree angle. In a traditional wet-sump design, the oil migrates all over the bottom of the engine. When it moves away from the pickup, there’s an excellent chance the pump will be temporarily starved.”
With a 7000-rpm redline and highly stressed internal components, oil-pressure fluctuations are intolerable. The dry sump carries most of its eight-quart supply of Mobil 1 (two quarts more than the LS2 V8’s capacity) inside a six-inch-diameter, 24-inch-tall cylindrical reservoir, where it’s on call to lubricate vital engine parts. The LS7’s gerotor-type (pronounced GEE-rotor) oil pump is a two-stage design driven by the forward portion of the crankshaft. (Wet-sump systems use a single-stage oil pump.) One stage, supplied by a hose connected to the reservoir, is responsible for pumping oil pressurized to 60 psi through the filter and cooler before it returns to the block to lubricate other components. The second stage scavenges oil that drains back to the sump and delivers it through a second hose to the remote reservoir located just behind the Z06’s right front tire. In addition to the external hoses, oil is routed through passages cast integrally with the LS7’s aluminum sump.
The storage reservoir is one clever piece of engineering. It consists of two aluminum castings welded and bolted to a thin-wall extruded-aluminum tube. Oil from the engine enters the bottom, squirts up through an internal tube, and spills down along the tube’s inside wall when it reaches the upper casting’s radial drain holes. This circuitous route separates entrained vapors (bubbles) and dispenses heat.Windage caused by the spinning crankshaft never has a chance to stir air into the lubricant.
Thanks to the dry sump, Z06 owners are able to exercise their herd of horses, confident that every pony is well lubed.