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Dry Sump Oiling System
The LS7 has a dry-sump oiling system designed to keep the engine properly lubricated during the high cornering loads the Corvette Z06 is capable of producing. An engine compartment-mounted 8-quart reservoir delivers
oil to the engine
oil pump under the demanding conditions of cornering loads in excess of 1 g.
Oil circulates through the engine and down to the oil pan, where it is sent back to the reservoir via a scavenge pump. The large-capacity reservoir, combined with a high-efficiency air-to-oil cooler, provides necessary engine oil cooling under the demands of the engine’s power output. With the dry-sump system, oil is added to the engine via the reservoir tank – which includes the oil level dipstick.
The LS7’s dry-sump system was developed and tested on racetracks in the United States and Europe , including Germany ’s famed Nürburgring. And while common in racing cars, the Corvette Z06 is one of just a handful of production vehicles – and the only production Corvette – to ever incorporate such a high-performance oiling system.
Cylinder Heads
The LS7’s CNC-ported aluminum cylinder heads are all-new and designed to meet the high airflow demands of the engine’s 7.0-liter displacement. Airflow has increased 25 percent compared to the base Corvette’s 6.0-liter LS2 V-8.
To ensure optimal, uninterrupted airflow, the LS7 has straight, tunnel-like intake runners. Very large by production-vehicle standards, the ports are designed to maintain fast airflow velocity, providing excellent torque at low rpm and exhilarating horsepower at high rpm. Their design is yet another legacy of the Corvette C5R racing program.
The heads feature 70-cc combustion chambers that are fed by huge, 56-mm-diameter titanium intake valves. The lightweight titanium valves each weigh 21 grams less than the stainless steel valves used in the LS2, despite the valve head having 22 percent more area. They are complemented by 41-mm sodium-filled exhaust valves (vs. 39.4-mm valves in the LS2). To accommodate the large valve face diameters, the heads’ valve seats are siamesed; and, taken from experience with the engines of C5R racecars, the LS7’s valve angles are held at 12 degrees – vs. 15 degrees for the LS2 – to enhance airflow through the ports.
“The heads are simply works of mechanical art,” said Muscaro. “We left nothing on the table when it came to ensuring the best airflow through the engine.”
Complete CNC porting of each cylinder head is performed on state-of-the-art five-axis milling machines, which carve out the intake ports, exhaust ports and combustion chambers with mathematical precision. In comparison, the LS2 features cast aluminum heads that require minimal finishing operations.
Camshaft, Exhaust & Other Features
A unique hydraulic roller camshaft actuates the large valves, giving them the time needed to bring in the air/fuel mixture and clear out the exhaust from the LS7’s large air passages. Based on C5R racing experience, the LS7’s cam has an all-new profile that provides .591-inch lift (15 mm) on both the intake and exhaust valves – almost .066 inch more than the LS2’s already stout .525-inch lift specs.
To accommodate the extremely high valve lift and the large ports, 1.8:1 roller rocker arms – offset on the intake side – and raised valve spring seats are used. In contrast, the LS2 has 1.7:1 conventional roller rockers.
Like other Gen IV V-8 engines, the LS7 uses a composite, three-piece friction-welded intake manifold, although its passages are tuned to support the engine’s considerable airflow requirements. The manifold is fronted by a 90-mm-diameter single-bore, electronically controlled throttle body. Higher-capacity, five gram/sec fuel injectors also are mounted in the manifold assembly. Like the LS2, the LS7 has a returnless fuel system that enhances both power and emissions performance.
On the exhaust side, racing-style hydroformed steel tubular exhaust headers are used. The individual header tubes meet at a special quad-outlet collector flange at the very tip of the header outlet where they smoothly enter into a “wide-mouth” catalytic converter. This system design approach greatly contributes to the Z06’s backpressure. The four rectangular sections of the flange smooth the exhaust flow out of the engine.
Hydroformed exhaust headers are unique to the LS7 and are a specialty even among racing engines.
Built By Hand
Assembly of every LS7 engine is performed by hand by a dedicated team member at GM’s new Performance Build Center . The engines are pushed through approximately 15 sub-assembly stations, where only the components and tools necessary to complete the station’s task are on hand. Tools such as electric torque wrenches provide repeatable accuracy for the engine’s precise tolerances, while the eyes of the specially trained team members provide intangible attention to detail.
Team members are engine-build specialists selected from GM’s experimental engine lab, and they complete about 30 LS7 engines per day. Upon completion, each engine is balanced and subjected to a 20-minute heat test. It is then transported to the Corvette Assembly Plant in Bowling Green , Ky. , to be married with a new Corvette Z06.
LS7 at a Glance
* Engine type cam-in-block 90-degree V-8
* Block configuration cast aluminum with pressed-in cylinder sleeves and 6-bolt, forged steel main bearing caps
* Bore x Stroke (mm / in) 104.8 x 101.6 /4.125 x 4.00
* Displacement (L / cu in) 7.0 / 427
* Crankshaft forged steel
* Connecting rods forged titanium
* Pistons cast aluminum
* Compression ratio 11.0:1
* Cylinder heads CNC-ported aluminum; 70-cc chamber volume
* Valve size, intake (mm / in) 56 / 2.20 (titanium)
* Valve size, exhaust (mm / in) 41 / 1.61 (sodium-filled)
* Camshaft hydraulic roller; 15 mm (.591 in) lift (intake and exhaust)
* Rocker arms 1.8:1; offset (intake only)
* Air intake composite manifold with 90 mm single-bore throttle body
* Fuel Premium required. 91 octane minimum
* Horsepower 500 (373 kW) @ 6200 rpm
* Torque (lb-ft) 475 (644 Nm) @ 4800 rpm
* Engine redline (rpm) 7000