[NEWS] Small-Block Celebrates 50 Years Powering the Automotive World

[Ken]

From TruckSeries.com:

Small-Block Celebrates 50 Years Powering the Automotive World

The unequaled legacy of the original Chevy small-block engine has left an indelible mark on the global auto industry and American automotive culture the past 50 years. Its impact on racing, from grass roots to the world stage, also has immensely touched those so passionate to their sport.

In 2005, GM celebrates this important industry milestone with the market launch of Gen IV small block V-8, available on four different GM models.

The 50th anniversary year may provide many story opportunities that illustrate how the small block engine has touched, inspired and powered those who love their cars.

Some of the Small-block's noteworthy milestones include:

• 1955: Small-block V-8 introduced in 1955 Chevrolets.
• 1957: Larger bore increased displacement to 283 cubic inches; Ramjet mechanical fuel injection was introduced, bringing horsepower to 283 - one horsepower for every cubic inch.
• 1962: Displacement increased to 327 cubic inches, with Ramjet fuel injected version rated at 360 horsepower.
• 1964: Cylinder head improvements bump the 327's highest horsepower rating to 375 with fuel injection.
• 1967: Little-known option Z28 released for the Camaro, which includes a high-revving 302-cubic-inch small-block for competition in SCCA Trans Am road racing.
• 1968: A Camaro Z28 wins the Trans Am championship; a 350-cubic-inch (5.7 liters) version of the small-block debuts and would become the quintessential small-block variant.
• 1970: 350-cubic-inch LT1 debuts in Camaro and Corvette and is rated at 370 horsepower; 400-cubic-inch small-block is offered - the largest-displacement small-block built.
• 1975: With fuel economy prevalent in consumers' minds, a more efficient 262-cubic-inch small-block is introduced.
• 1978: V-6 engine based on small-block design introduced; it would become the Vortec V-6 truck engine more than a decade later.
• 1980: Last year for the 400 small block.
• 1982: Fuel injection reintroduced with the Cross-Fire injection system on Corvette and the redesigned Camaro Z28.
• 1985: Tuned port fuel injection replaces Cross-Fire Injection, ushering in the modern era of electronically controlled, port-injected engines.
• 1986: Aluminum cylinder heads debut as standard equipment on Corvette; block changed to accept new single-piece rear main seal.
• 1987: Hydraulic roller lifters introduced.
• 1989: The H.O. 350 "crate engine" is developed, offering a ready-built performance engine from the factory. It would change the way hot rodders approach engine building in the next decade.
• 1992: LT1 engine in the Corvette introduces Gen II small block design, which features reverse-flow cooling, revised cylinder head design, and crank-triggered optical distributor.
• 1996: Vortec V-8 engines introduced in trucks, featuring cylinder heads with swirl-inducing combustion chamber design to increase power and torque.
• 1997: Gen III 5.7-liter LS1 small-block introduced with all-new Corvette, featuring all-new deep-skirt block casting with six-bolt mains; redesigned cylinder heads with symmetrical ports and combustion chambers; and coil-near-plug ignition system.
• 1999: Gen III-based Vortec V-8 engines introduced in GM trucks; displacements include 4.8 liters, 5.3 liters and 6.0 liters.
• 2005: Gen IV small-block introduced 50 years after the original. Available in: Chevrolet TrailBlazer EXT, GMC Envoy XL and Envoy XUV with fuel-saving Displacement on Demand (DOD) technology; or in the Chevrolet Corvette without DOD.

More than power or displacement, the significance of the small-block has been its adaptability as market demands and technology evolved during the past five decades. Engineers have met every challenge and kept the small-block on the leading edge of performance.

The introduction of the Gen IV engine signals the small-block's legacy will extend into the future.

 

[Ken]

[NEWS] New Corvette Engine Shatters Previous OHV RPM Limits

From I-Newswire.com:

New Corvette Engine Shatters Previous OHV RPM Limits

PONTIAC, Mich. - GM engineers have achieved a feat many speculated was not possible. The new LS7 7.0-liter OHV (overhead valve) V-8 engine for the 2006 ZO6 Corvette will not only achieve 500 horsepower but will be capable of running up to 7100 rpm. The previous limit was 6600 rpm in the 6.0-liter LS2.

i-Newswire, 2005-02-11 - With this new engine GM is showing multi-valve overhead cam performance is achievable with a two-valve cam-in-block engine. For the new ZO6, higher rpm allows the driver to remain in first gear to just over 60 mph, contributes to higher top speed and improves overall vehicle performance. The LS7 is one of the first automotive OHV production engines in the industry capable of over 7000 rpm.

The new ZO6's sub four-second 0-60 mph time is achieved in part by the extended rpm range and the ability to remain in first gear past 60 mph. The over-190 top speed of the ZO6 is partially due to the speed capability of the engine. As aerodynamic drag becomes a factor at higher speeds, the capability to run higher rpm allows the transmission to be run in a lower gear generating more effective torque at the rear wheels. Also, having the ability to shift all gears at higher speeds improves elapsed times whether on a road course or drag strip.

"For a production engine to run at this high of an rpm blurs the lines even more between OHV and OHC ( overhead cam ) design," said Dave Muscaro, assistant chief engineer for small block engines. "We took a complete systems approach to achieve the high rpm. We have a tight valvetrain design along with some race-inspired materials for the reciprocating components like titanium intake valves and connecting rods."

OHV engines use pushrods to activate the valves via rocker arms, whereas with OHC engines the valves are typically actuated directly via finger followers. The extra mechanical movement and weight of the components of an OHV valvetrain present challenges to higher rpm. The LS7 design and use of lightweight, stiff components, along with GM's economy of scale, make higher rpm obtainable in a production OHV engine.

"The new LS7 cylinder head gave us the opportunity to design a new high-revving valvetrain," said Jim Hicks, LS7 valvetrain design engineer. "The new valvetrain had to be as stiff and light as possible to assist meeting the engine's aggressive performance targets without compromising idle quality and low emissions. Stiffness is increased with larger diameter pushrods and rocker arms optimized through extensive finite element analysis."

The LS7's 1.8:1 rocker arm ratio and titanium intake valves contribute to a lower effective mass ( compared to the LS2 base Corvette engine ) in spite of larger and stiffer valvetrain hardware. Idle quality and emissions performance is achieved with the help of a more aggressive cam that provides more lift and duration while still keeping overlap area to a minimum.

"We consulted with our Motorsports group on numerous design aspects of the cylinder head design, said Hicks. "We adopted some of the latest ideas that have been successful in the Nextel Cup and the American Le Mans Series including valve centerline positions, valve angles, valve sizes and rocker arm ratio."

Due to the relatively large bore and stroke ( 104.8 x 101.6mm ) of the LS7, light weight pistons, piston pins, titanium rods and a steel crankshaft are also used to achieve extended rpm. The flat top pistons with race-ready valve reliefs are 482 grams each and use a shortened lightweight piston pin. Each forged titanium rod weighs only 464 grams which is almost 30 percent less than each rod in the LS2. The forged steel crankshaft is stronger, stiffer and designed to handle high-speed loads.

General Motors Corp. ( NYSE: GM ), the world's largest automaker, has been the global industry sales leader since 1931. Founded in 1908, GM today employs about 324,000 people around the world. It has manufacturing operations in 32 countries and its vehicles are sold in 200 countries. In 2004, GM sold nearly 9 million cars and trucks globally, up 4 percent and the second-highest total in the company's history. GM's global headquarters are at the GM Renaissance Center in Detroit. More information on GM can be found at [color=#80000]www.gm.com.[/color]