Inside the LS7
The all-new LS7 in the 2006 Corvette Z06 reintroduces the 427-cubic-inch engine to the Corvette lineup. Unlike the previous 427 engine, which was a big-block design, the new 7.0-liter LS7 is a small-block V-8 - the largest-displacement small-block ever produced by Chevrolet and GM, and a tribute to its 50 years as a performance icon.
With 505 horsepower (377 kw) and 470 lb.-ft. of torque (637 Nm), it also is the most powerful passenger car engine ever produced by Chevrolet and GM. The LS7 is easily identified under the hood by red engine covers with black lettering. The LS7 shares the same basic Gen IV V-8 architecture as the Corvette's 6.0-liter LS2, but it uses a different cylinder block casting with pressed-in steel cylinder liners to accommodate the engine's wide, 104.8-mm-wide cylinder bores. Compared with the LS2, the LS7 also has a different front cover, oil pan, exhaust manifolds and cylinder heads - among many other components.
Internally, the LS7's reciprocating components make use of racing-derived lightweight technology, including titanium connecting rods and intake valves, to help boost horsepower and rpm capability. The rpm fuel shut-off limit is 7000 rpm. The LS7's details include:- Unique cylinder block casting with large, 104.8-mm bores and pressed-in cylinder liners
- Forged steel main bearing caps
- Titanium connecting rods with 101.6-mm stroke
- Cast aluminum flat-top pistons
- Racing-derived CNC-ported aluminum cylinder heads with titanium intake valves and sodium-filled exhaust valves
- Low-restriction air intake system
- Hydroformed exhaust headers with unique "quad flow" collector flanges.
One of the clearest examples of the LS7's race-bred technology is its use of titanium connecting rods. They weigh just 464 grams apiece, almost 30 percent less than the rods in the LS2 V-8. Besides lightweight, which enhances high-rpm performance and rpm range, titanium makes the rods extremely durable.
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, as it ingests approximately 100 cubic feet more air per minute than the Corvette's 6.0-liter LS2 V-8 - an 18-percent increase in airflow. Consequently, a hydraulic roller camshaft with .591/.591-inch valve lift is used to allow plenty of air to circulate in and out of the engine.
To ensure optimal, uninterrupted airflow, the LS7's heads have straight, tunnel-like intake runners. Very large by production-vehicle standards - even racing standards - they are designed to maintain fast airflow velocity, providing excellent torque at low rpm and exhilarating horsepower at high rpm. The heads feature 70-cc combustion chambers that are fed by huge, 56-mm-diameter titanium intake valves. The lightweight titanium valves weigh 21grams 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 C5-R racecars, the LS7's valve angles are held at 12 degrees - vs. 15 degrees for the LS2 - to enhance airflow through the ports.
The LS7 has a dry-sump oiling system designed to keep the engine fully lubricated during the high cornering loads the Corvette Z06 is capable of producing. An engine compartment-mounted 8-quart reservoir delivers oil at a constant pressure to a conventional-style oil pump pick-up at the bottom of the engine. The pressurized oil feed keeps the oil pick-up continually immersed in oil at cornering loads exceeding 1 g.
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