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small-block v-8

Since it was introduced in 1955, the Chevrolet Small Block has consistently featured a compact, efficient 90-degree V-8 design, with overhead valves, pushrod valvetrain, and 4.4-inch on-center bore spacing.GM

General Motors has built more than 100 million "small-block" V-8s since introducing the legendary motor family in 1955 to do battle in Detroit's escalating horsepower war.

Since then, small-block V-8s have powered family sedans, arriving in time for the iconic '55 Chevys and later the Malibu SSs and Camaros of the 1960s – and Le Mans winners, giving Corvette its first class win in 1960 and seventh in 2011, along with countless other forms of competition machines from NASCAR stockers to drag racers. And just about every other type of vehicle requiring some V-8 muscle GM has built up to and including the 2012 model year. With a new generation in the planning, they'll be around for a while to come.

Small-block power has ranged from the original's 162 hp up to the 638 hp generated by the 100-million-milestone engine, a fourth-generation LS9. The most powerful production version, the LS9 powers the 330-km/h ZR1 Corvette and, in mere 580-hp LSA form, the ZL1 Camaro currently being put together in GM's Oshawa, Ont., plant.

Chevrolet built the corporation's first V-8 in 1917, a 55-hp, 288-cubic-incher, but less than 3,000 were produced. The story of the small-block begins four decades later with the arrival of Ed Cole, fresh from overseeing the design of Cadillac's new V-8, as Chevy's chief engineer in 1952.

Chevrolet had a V-8 in the works, too, but Cole – described as brilliant, charismatic and at times autocratic – shifted into the latter mode after seeing the plans and pulled the plug on this effort. His V-8 vision was a compact, lightweight and, above all, powerful design and he pulled together a GM engineering dream team to realize it.

What it created was an overhead valve V-8 that was ahead of its time but apparently timeless. It's still being built, half a century later, in original gen-one form for industrial and marine use, and as special "crate motors" of up to 454 cubic inches by Chevrolet Performance for racers and hot-rodders. The basic architecture created in the early 1950s has survived four generations of development and is heading into a fifth.

At its heart is the engine block, the structure incorporating the cylinder bores. Innovative design and newly developed casting techniques allowed this to be compact (just 21.75 inches long by nine inches tall) but tough and lightweight, and more cost-effective to produce. The small-block engine at 531 pounds fully dressed would end up 41 pounds lighter than Chevy's old standby, the "Stovebolt" six.

It was this block that eventually gave the engine family the "small-block" name, which doesn't relate to displacement, as production small-blocks were made as large as 427 cubic inches.

It seems to have acquired the small-block moniker after GM's larger and heavier "big-block" arrived in 1958. Among those racing early versions, the over-achieving small-block was often referred to as the "Mighty Mouse" – later shortened to just "Mouse" – while the big-block became the "Rat."

Coles' think tank of engineering talent also came up with a system to meter oil through hollow pushrods that lubricated newly developed and cheap-to-make lightweight stamped steel rocker arms that allowed the engine to achieve high rpm.

The cylinder heads had efficient wedge combustion chambers that encouraged these higher revs from a short-stroke design with a 3.75-inch bore and 3.0-inch stroke that gave the original version a displacement of 265 cubic inches. A forged steel crank and connecting rods (the latter tested to 18 million cycles) ensured it would all hold together when those high revs were employed. Helping too was individual balancing of parts to ensure smooth operation.

And obviously a lot of thought went into the one-piece intake casting that incorporated the cooling water outlet, exhaust heat riser, distributor mounting, oil filter and the lifter valley covers.

The original 265-cubic-inch small-block offered in 1955 Chevy's made 162 hp – compared to the hottest Stovebolt in the first Corvettes 150 hp – but hotted-up with a Power Pack that included four-barrel carb and dual exhausts 180 hp. A year later, an optional Turbo-Fire was producing 205 hp and the version slotted into the Corvette 225 hp at 5,200 rpm and 270 lb-ft of torque at 3,000 rpm, finally giving it performance to match its looks.

And the small-block just got better and bigger, growing to 283 cubic inches in 1957 and becoming, when fitted with Rochester fuel injection, one of the first engines to produce more than one horsepower per cubic inch. It won the NASCAR championship that year and was banned for the next.

A number of variants followed; the 327 in 1962, then the 350, 302 of Trans Am fame, a 307 and the 400 in 1970. A small 262-cubic-incher made a brief mid-'70s appearance, its 110 hp the lowest rating for the small-block, and the 305 in 1976 that served until the end of the century.

Small-blocks are currently produced in Mexico, the United States and have been made for many years in Gen-4 form at GM's St. Catharines, Ont., plant, which is also scheduled to produce the upcoming fifth generation.

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