How to Build Killer Chevy Small-Block Engines. Mike Mavrigian
to as Turbo-Fire or High Torque engines. The 350-ci engine, one of many iterations of the platform, was introduced in 1967 and helped the small-block Chevy become one of the most popular platforms for performance use. The 350 is widely considered as the standard platform for the small-block family.
The 265-ci engine debuted in 1955 and was the foundation for decades of performance that followed. (Photo Courtesy GM Media Archives)
The 1965 327-ci engine with fuel injection is shown. The Rochester Ramjet fuel injection system was first offered as a high-performance option on the Corvette and GM passenger cars in 1957. It was discontinued partway through 1965 in favor of the Chevrolet big-block as a performance option. This is a purely mechanical system, unlike modern electric systems today. (Photo Courtesy GM Media Archives)
Shortly after the debut of the small-block engine, the aftermarket began introducing components that were primarily designed to work with the OEM factory blocks to improve performance. Beginning with upgrades to camshafts, intake manifolds, carburetors, and tubular exhaust headers, hot rodders and racers began to experience and enjoy substantial performance improvements. This continued with upgraded cylinder heads in both cast iron and aluminum, forged pistons of various dome configurations, superior ignition components, stronger valvetrain components, stronger connecting rods, stronger crankshafts, stronger main caps, different crank strokes and connecting rod lengths, etc.
As racers continued to stretch the engine speed and load parameters, weak links that became apparent were quickly addressed, resulting in increasingly stronger parts in addition to components and systems that offered power enhancements. Since those early days, the small-block Chevy engine became firmly established as the standard of performance engines for street rodders, drag racers, oval track racers, and road racing competition. Aftermarket manufacturers also began producing stronger engine blocks that offered superior strength, rigidity, and cooling, in addition to providing the ability to increase cylinder bore diameters and to accept longer crankshaft strokes. In the effort to reduce weight and to improve cooling, aluminum blocks became available for specific racing applications.
General Motors continued to evolve engine platforms from the early 1970s’ LT1 and later LS-series designs to the current LT platforms, but despite this ever-evolving development of newer and more sophisticated platforms, the performance industry never abandoned the venerable Generation I small-block. It was just the opposite: development continues to this day to address the needs of enthusiasts and racers who steadfastly continue to take advantage of this engine platform.
The SBC has long been considered an iconic symbol of American performance, representing a standard to which all other V-8 engines are compared. In other words, the small-block (Gen I) Chevy engine was, and continues to be, an established workhorse and is unlikely to ever fall by the wayside. Taking advantage of all that the performance aftermarket industry has to offer, today’s builders are able to create 1,000-plus-hp beasts. One of the greatest benefits to consider is that everything you need or want is readily available. It all boils down to how much you want to spend.
Displayed is the infamous 302-ci high-winding engine that powered the iconic 1969 Camaro Z28. This engine was created in 1967 specifically to meet SCCA rules for Trans Am racing The 302 is the byproduct of dropping a 283 crank into a 327 block. (Photo Courtesy GM Media Archives)
The early small-block 265 engines featured a 3.00-inch stroke and 3.750-inch bore that produced around 162 hp and about 257 ft-lbs of torque when equipped with a 2-barrel carburetor. The 283 engine moved up to a 3.875-inch bore and increased power to 185 hp. When fitted with dual 4-barrel carbs, a higher compression ratio of 9.5:1, and dual exhaust, the power level rose to around 270 hp. In 1962, the 327-ci design debuted, featuring a 4.00-inch bore and 3.250-inch stroke with OEM power levels that reached the 340-hp level (360 hp at 11.25:1 compression in the injected Vette version). Along came the 302 engine, famous for its application in the 1969 Camaro Z28 that offered around 370 to 465 hp, depending on the intake and fuel setup.
While the basic design platform for the small-block Chevy engine hasn’t changed significantly, the performance aftermarket continues to develop components and procedures for boosting power and torque.
Thanks to ongoing aftermarket development, today you can configure a small-block Chevy for just about any application and degree of power. This example is a 422-ci build, featuring 100-percent performance aftermarket components that easily spit out over 700 hp.
Stronger and more efficient blocks, cranks, rods, threaded fasteners, and main caps have been developed to withstand today’s demands for extreme power and torque. Assembly methods have changed as well with builders paying closer attention to real-world connecting rod bolt stretch as opposed to following torque specs.
Along came the 350 small-block in 1967, and the die was cast. The 350 became the go-to standard platform for performance applications. The original crank stroke was 3.480 inches and was coupled with 4.00-inch bores. With a variety of bore and stroke combinations, cubic inch displacement choices grew. Yes, you can alter bore and stroke on any engine, but the 350 became extraordinarily popular as a basis of performance mods. The following chart provides examples of combinations.
OEM Crankshaft Journal Size
Be aware that Chevy small-block versions were initially available with different crankshaft rod and main journal sizes. Early 265 through 327 engines featured small journal cranks, while later versions featured medium journals, and the 400 version featured what is referred to as a large journal.
To provide a boost in cubic inches, and in an effort to make more torque, General Motors debuted the 400-ci version of the small-block in 1970. This block featured siamesed bores that provided more strength but reduced cooling efficiency. The bore was 4.125 inches and the stroke was 3.750 inches. The 400 crank also featured a larger 2.650-inch main journal as opposed to the 350’s 2.450-inch mains.
Weight-reduced aluminum blocks are readily available for the SBC for replacement of the OEM design as well as specialty applications and for weight savings and superior cooling.
One of the most popular engine platforms for professional Sprint car racing continues to be the SBC designed for running alcohol fuel.
| CI | Bore | Stroke |
| 355 | 4.030 | 3.480 |
| 364 | 4.000 | 3.622 |
| 383 | 4.030 | 3.750 |
| 402 | 4.125 | 3.760 |
| 408 | 4.030 | 4.000 |
| 410 | 4.135 | 3.820 (one example) |
| 422 | 4.165 | 3.875 |