Around the Block

The Foundation of Your Engine Is a Modern Marvel

Photography by Jeff Smith

Hot rodders know them as V-8s, V-6s, in-lines, or even horizontally opposed, but no matter how they're configured the engine block in your car is the foundation of its power. For this month's "How it Works," we'll discuss the many facets of modern engine blocks and how today's technology has improved them for better performance. Granted, we'll base our discussion largely around Chevrolet engines, but the principles apply to any reciprocating engine.

Whether your performance engine of choice is the basic small-block Chevy, big-block, or one of today's aftermarket offerings with billet caps and aluminum construction, the cylinder block determines the basic structure of the engine. The engine block is formed to contain a specific number of cylinders and pistons, retain the crankshaft, and camshaft (except for overhead cam motors), lubrication system, water cooling passages, and mounting for cylinder heads and auxiliaries such as the starter, fuel pump, and accessory brackets.

Since the engine block is a massive casting, precision machining is critical to its function. Inside the block, each cylinder is bored and honed to a specification with minor variation. As an example, a new 350 small block with its 4-inch bore is manufactured with an actual production diameter that spans 3.9995- to 4.0025-inch. Such a close tolerance with a very accurate circular shape is critical to preserving cylinder pressure during engine operation, while minimizing friction and wear as the piston moves up and down in the bore.

In cast-iron blocks, cylinder bores are machined into the block's casting, but in many newer designs the block is cast from lightweight aluminum. These lighter blocks require cast iron cylinder liners (sleeves) installed into each bore to provide high wear resistance. After the liners are installed into each position, they are finished to specification ensuring roundness.

In a four-cycle engine, four-cylinder engine, every two revolutions of the crankshaft (720 degrees) produces four power strokes (one per every 180 degrees). So if there are only two cylinders, there are only two power strokes or one per 360 degrees. This example illustrates that if there are more cylinders, the combustion explosions will occur closer together and the engine will generally operate smoother. This is why a V-8 engine typically operates more smoothly than a V-6 engine.

The number and the arrangement of cylinders classifies the engine. When cylinders are arranged in a straight line the engine is called an inline type. These engines are usually even number designs such as four- or six-cylinder configurations. But recently, GM has introduced an in-line five-cylinder engine, the Vortec 3500 I5 Inline engine, which provides impressive power, fuel economy, and smoothness.

An engine such as a Chevrolet 350 or 454 is made into a V shape with the same number of cylinders arranged in line on both banks. On these V-type engines, both banks slant toward a common crankshaft. Besides the common V-8 and V-6 engines, there are also V-10s, V-12s, and V-4s available from many different manufacturers. One of the most notable (and huge) modern V-type engines is the '03 Cadillac Sixteen concept with its 830-cubic-inch, 1,000 horsepower V-16 powerplant. But large engines are nothing new at Cadillac. During the difficult car climate of the 1930s, Cadillac produced a 368-cubic-inch V-12 and 453-cubic-inch V-16.

The cylinder's bore diameter, the amount of cylinders, and the length of the stroke determine the engine's displacement. An engine's approximate displacement can easily be attained by multiplying bore x bore x stroke x number of cylinders x 0.7854. So if we have an engine with a 4-inch bore and a 3.48-inch stroke we simply multiply 4.00 x 4.00 x 3.48 x 8 x 0.7854 and we have 349.848, which we round to 350 cubic inches. Or if we use a new Corvette LS2 engine as an example with a 101.6mm bore and a 92mm stroke, we can find the metric displacement by multiplying 101.6 x 101.6 x 92.0 x 8 x 0.7854, which equals approximately 5,967 cubic centimeters (6000) or 6.0 liters.

The great news about engine blocks for hot rodders is that the industry is constantly striving to deliver better and lighter blocks that provide tremendous foundations to produce even more power than before. Today's blocks are more rigid and often lighter than before and most times come in configurations unheard of just a few years ago.