Secrets of the Small Block’s Success
Ten reasons the original small-block engine was an engineering triumph
29.11.2011
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WIXOM, Mich. – General Motors has built the 100 millionth example of its small-block engine. The milestone came 56 years after the first production engine and represents the fourth generation of the iconic engine family. That’s quite a legacy in an industry where the typical lifespan of an automotive engine can be a dozen years or less.
All generations of GM’s small-block family have featured a cam-in-block architecture and a 4.4-inch bore center specification – the center-to-center distance between the cylinders. And while GM didn’t invent the basic design of the small block engine, it interpreted them in a way that made it immediately successful. In fact, those traits were recognized at its introduction in 1955 in a paper presented at the Society of Automotive Engineers (SAE) Golden Anniversary Annual Meeting in Detroit, on January 12, 1955.
Authored by chief passenger car chassis design engineer R.F. Sanders, the paper was titled “The New Chevrolet V-8 Engine,” and provided essential details of the small block’s design, manufacturing and packaging. As described by Sanders in his paper, here are the top ten reasons for the original small-block’s success:
1. Compact size: “Anything we could slice off the top or bottom of the block, or from the bores, would mean less heavy iron and less water required to cool it,” Sanders wrote. “This was one of our prime objectives – to make that basic block just as compact and as light in weight as possible.”
The original small-block was indeed a very tidy package. Its block was 21.75 inches long (552 mm) and only nine inches tall (228 mm), from the oil pan rail to the cylinder heads.
2. Light weight. The total weight of the new small-block V-8 was 531 pounds (241 kg) – 41 pounds (18 kg) less than the inline-6 engine it replaced in Chevrolet’s lineup.
3. Manufacturing simplicity. The original engine’s block required only twelve casting cores; overhead valve V-8s from competing manufacturers used as many as 22 cores.
4. Innovative design. The key to the small-block’s high-speed performance was an innovative valvetrain, which featured stamped steel rocker arms pivoting on individual studs. Most other V-8 engines of the time used heavy, complex rocker arm shafts.
5. Efficiency. The small block’s creators selected a high-turbulence, wedge-type combustion chamber design that provided a smooth rise in cylinder pressure and minimized the engine’s octane requirement. The wedge-shaped chambers required no machining (except for valve seats), and permitted the use of lightweight and inexpensive flat-top pistons.
6. Trouble-free Lubrication. The small block’s oiling system eliminated external lines and high-pressure oil feeds to the cylinder heads. This feature prevented potential leaks and simplified engine assembly.
7. Smoothness. Rotating and reciprocating components were balanced individually; then the entire assembly was final balanced to within ½ in.-oz. on a special fixture that rotated the engine.
8. Reliability. Chevy engineers used premium materials, such as forged steel crankshafts and connecting rods, to bolster the small block’s durability. The connecting rods were tested to 18,000,000 cycles without failure.
9. Breathing. The small block’s interchangeable cylinder heads featured an efficient cross-flow port design that remained popular with racers more than 40 years after it was introduced. Five head bolts were arranged in a pentagonal pattern around each cylinder to minimize local cylinder bore distortion and lower stress.
10. Ingenuity. The Chevrolet design team made components serve a variety of functions. For example, the hollow pushrods actuated the valves and carried oil to the cylinder heads. The one-piece intake manifold combined the water outlet, exhaust heat riser, distributor mounting, oil filter and the lifter valley cover in a single casting.
About General Motors
General Motors Co. (NYSE:GM, TSX: GMM) and its partners produce vehicles in 30 countries, and the company has leadership positions in the world's largest and fastest-growing automotive markets. GM’s brands include Chevrolet and Cadillac, as well as Baojun, Buick, GMC, Holden, Isuzu, Jiefang, Opel, Vauxhall and Wuling. More information on the company and its subsidiaries, including OnStar, a global leader in vehicle safety, security and information services, can be found at http://www.gm.com.
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