It's new, powerful, and packed with the latest technology. In 1955 those words described the first small-block Chevy, the 265, with its passenger car rating of 162hp. Soon after the first 265s hit the showrooms, customers sought even more performance and Chevrolet responded with the 283 in '57 and then the 327 in '62. By the late '60s, high-winding 302 engines and powerful 350s continued the trend. By '70, Chevrolet released the big-inch 400 small-block. Later, custom bore and stroke 365 small-blocks, 377, 383, and 406 displacements appeared on the hot-rodding scene.
Today, Vortec and LS-series engines are excellent performers and provide very acceptable fuel economy. The most powerful factory small-block Chevy so far (the '06 427ci LS7 engine) boasts titanium rods, a dry-sump oiling system, an all-aluminum block and heads, and 505 horses. This LS7 small-block will shove an '06 Z06 Vette from 0 to 60 mph in 3.5 seconds, cover the quarter-mile in 11.50 seconds, and continue on to 195 mph; and it's EPA rated at 26 mpg on the highway. Who said good gas mileage cars are boring?
What this all means is that the small-block Chevy has both a tremendous history and a spectacular future. GM has estimated that through 2005, more than 90 million small-block Chevys have been produced. Here we'll chronicle the benchmarks, how hot-rodding has improved power over the years, and where GM development is currently headed. Better cylinder heads, carburetion, fuel injection, improved bore and stroke relationships, and more have all been directed at the engine that is arguably the most hot-rodded in the world. As always, the small-block Chevy is powerful and packed with technology.
Efficient Design With the Gen I
In the early '50s, Chevrolet engineers specifically designed the small-block engine in a compact size to allow a streamlined production process. New innovations, such as greensand casting, meant the block could be cast upside down, thus reducing the amount of cores. The small size of the block provided an economical use of iron and required less cooling effort in service. To provide high-rpm operation, engineers designed lightweight rocker arms from stamped steel. The 265 engines used a 3.00-inch stroke and a 3.75-inch bore. The new small-block's cylinder heads with a cross-flow port structure and wedge combustion chambers allowed for a broad powerband. The new small-block engine was designed with 4.4-inch bore centers (measured as the center of one cylinder to the next) and is the same dimension carried through to the Gen III small-block designed in '97. Other new designs for the small-block Chevrolet included:
*Hollow pushrods to carry oil to the cylinder heads
*A one-piece intake manifold combining the water outlet, exhaust heat riser, distributor mounting, and lifter valley cover in a single component
*An internal oiling system
1 HP/CI Early On
Although at the upper end of engine options, dual quads had been offered on the 265 with a high-lift cam and 240 hp, the era demanded not only more power, but also broadband performance. So the new-for-'57 283 with its 0.125-inch larger bore (3.875-inch bore, 3.00-inch stroke) was available with the standard two-barrel, four-barrel, dual quads, or a new mechanical fuel-injection system that produced 283 hp from 283 ci (1 hp per cubic inch). All cylinder heads for the 265s and 283s used 1.72/ 1.50-inch valves.
For '62 Chevrolet's new hot motor, the 327 (the first small-block with a four-inch bore) packed a wallop. Besides the carbureted versions, a fuel-injected 327 with 360 hp was optional in the '62 Corvette. The cylinder heads used on this engine (and some others of the era) were the 3782461X head with 1.94/1.50-inch valves. These heads had the commonly found double-hump shape on the end of the head. It should be noted that beginning in '64 and through '68, cylinder heads with the double-hump shape also used 2.02-inch intake valves (aka fuelie heads). Castings with 2.02-inch intake valves were also used on the 365hp (Holley carburetion) and 375hp (Rochester fuel-injection) Corvette 327 engines. Except for some early truck applications, it would not be until '69 that all small-block cylinder heads would feature accessory mounting holes.