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PONTIAC, Mich. – Compact, powerful and packed with innovative technology – it’s an accurate description of the modern GM small-block V-8. Those words also were used to describe the original small-block when it debuted in 1955.

GM will introduce the Gen IV small-block V-8 50 years after the first small-block. It will be available in V-8-equipped models of the 2005 Chevrolet TrailBlazer EXT, GMC Envoy XL and Envoy XUV, offering fuel-saving Displacement on Demand (DOD) technology.

“The new Gen IV engine is the best example yet of the continuous refinement in performance and efficiency that has been part of the small-block’s legacy since day one,” said Sam Winegarden, chief engineer of small-blocks. “The small-block V-8 not only is a viable and relevant engine in today’s market, but technology such as Displacement on Demand demonstrates its adaptability in the face of evolving marketplace expectations.”

DOD has the capability of disabling the combustion process of half the engine’s cylinders in certain driving conditions, enabling fuel savings of 6 percent to 8 percent. The process is instantaneous and virtually imperceptible, and the engine delivers horsepower and torque bands comparable to previous non-DOD small-block engines.

A car version of the Gen IV engine without DOD will debut in the 2005 Chevrolet Corvette.

GM Powertrain estimates that by the end of the 2005 model year, more than 90 million small-block-based engines will have been produced since the original engine’s 1955 introduction.

Compact design
Contemporary demands for efficiency and performance refinements were the very demands that pushed the original small-block’s development 50 years ago. It started in the early ’50s with the planned replacement of Chevy’s sturdy, but antiquated, straight-six engine – a large, heavy powerplant commonly called the Stovebolt Six.

Although a new V-8 was on the drawing table when Chief Engineer Ed Cole transferred from Cadillac to Chevrolet in 1952, he soon dismissed the original design and challenged his engineers to develop a more compact engine that would be easier to manufacture. The overhead valve design had been a staple of the Stovebolt engine and, to some at GM, one of the Chevrolet cars’ selling points. Retaining that trait was agreeable with Cole, whose previous assignment was the design of Cadillac’s OHV V-8.

When completed the new V-8 engine had a minimalist design to take advantage of streamlined production techniques. Innovations like green-sand casting, which allowed the block to be cast upside down and dramatically reduce the number of cores, as well as lightweight stamped-steel rocker arms that allowed a much higher rpm range, were state of the art.

The new small-block’s cylinder heads were another important step forward. Their cross-flow port design and wedge-shape combustion chambers were very efficient and, when combined with the high rpm capability of the valvetrain, gave the new V-8 a broad performance band. Also, the engine’s quintet of head bolts around each cylinder provided superior cylinder head location. Other innovations included:

Hollow pushrods carried oil to the cylinder heads
A single-piece intake manifold combined the water outlet, exhaust heat riser, distributor mounting and lifter valley cover in a single component
Internal lubrication eliminated the need for external oil lines, greatly reducing the chance for leaks
Compact size required less iron to produce the engine and less water to cool it during operation.
The internal oiling system was a breakthrough not found on many other automotive engines at the time, especially in Chevrolet’s low-price field.

And though a seemingly inconsequential specification at the time, the new small-block engine also was designed with 4.4-inch bore centers – the distance from the center of one cylinder to the next. The design contributed to the engine’s compact size, but the dimension has come to symbolize the balanced harmony of the small block. It was the dimension around which the all-new Gen III small block was designed in 1997.

“The long history of the small-block is one of the reasons the new generation of engines is so powerful and efficient,” said Winegarden. “GM has almost 50 years of experience with its valve-in-head design, and that has provided immeasurable detail for keeping the small-block a viable, relevant engine for today and the future.”

A legacy of power and adaptability
With 3.75-inch bores and a 3.00-inch stroke, the first small-block displaced just 265 cubic inches (4.35 liters). Drawing its breath through a two-barrel carburetor, the base version produced 162 horsepower (gross); with a four-barrel, the engine was rated at 195 (gross) in the Corvette. Better still, it weighed nearly 50 pounds less than the old Stovebolt Six.

From that auspicious beginning, the small-block was at the forefront of technology. A fuel-injected version of the engine was available from 1957 through the mid-‘60s, and as the horsepower wars of the late ’60s raged, the small-block proved to be powerful ammunition for Chevrolet.

The small-block would grow to a maximum of 400 cubic inches and, with the 2004 Corvette Z06’s LS6 engine, produce 405 horsepower. In less glamorous, but perhaps more important roles, small-blocks served as quiet servants in untold millions of family cars and work trucks.

The small-block’s versatility also found a place in countless vehicles probably never considered by its designers. Everything from industrial equipment to marine applications of all sizes has used the GM small-block as standard equipment. It has become a staple of auto racing circuits of all types, too, and some industrious builders even have squeezed the engine into custom motorcycles.

When marketplace demands required more efficiency, the small-block was downsized to accommodate. But as engineers found new and better ways to extract power from the venerable engine, the small-block’s displacement and power increased while meeting – or exceeding – federal requirements for fuel efficiency and lowered emissions.

In 1978 engineers developed a V-6 engine from the original small-block’s architecture. Called the “three-quarters small-block” at the time, the engine lives on today in many GM trucks as the Vortec 4300 V-6.

In the early ‘90s, the Gen II small-block was introduced in high-performance cars including the Corvette and Pontiac Firebird Trans Am. Known as the LT1 and, later, the LT4, the Gen II featured new, low-friction internal components and reverse-flow cooling to enable the most powerful small-blocks since the heyday of the muscle car era. Some Gen II features, including the low-profile, high-flow, intake manifold, previewed technology that would be incorporated into the all-new Gen III.

The Gen III was introduced as the LS1 5.7-liter engine in the 1997 Corvette, while Vortec versions of the Gen III for trucks were introduced in 1999, with displacements ranging from 4.8 liters to 6.0 liters. The Gen III engine benefited from new technology and production methods, but its design drew upon more than 40 years of research and continuous improvements from the Gen I and Gen II small-blocks.

Continual improvements also drove the development of new efficiencies and power increases in the Gen IV small-block.

That legacy of the small-block has left an indelible mark on the global auto industry and American automotive culture. Some of its many 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.

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 for decades to come.

Premium Member
14,963 Posts
the 350 debuted in 1967 in the Camaro SS as the only car you could get a 350 in. It was later realized that this engine was the shiz, and was then given to the new Nova, and then vette... and then everything from hot rods to issuzu work trucks to the avanti.
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