Around the Block

The Foundation of Your Engine Is a Modern Marvel

Jeff Smith Dec 20, 2004 0 Comment(s)

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.

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This production small-block Chevy is cast-iron and features a 4.00-inch bore. This basic design is relatively short and basically rigid. Unlike many other manufacturer's V-8s, the small-block Chevy casting only drops 1/8-inch below the crankshaft's centerline. Chevrolet's engineering team in the early '50s did this to minimize weight and allow the main bearing caps to locate in a broached longitudinal slot. Small-block Chevys generally provide an economical foundation for many performance buildups.

A Chevy V-8 incorporates a full-pressure lubrication system with internal passages throughout the block. Engine oil from the pump travels through the filter into a 1/2-inch main gallery above the camshaft and then through a hole to the backside of the rear cam bearing.

Cam bearings are installed into the block with a special tool. For small-block Chevys, a set of cam bearings will contain three different sizes that vary by the outside diameter, typically marked on the back. Install them in the wrong order and your camshaft will not fit into the block.

World Product's Motown block features high-density cast-iron and is reinforced in all critical areas. The front and rear bulkheads are substantially thicker than stock and the reinforced main webs accept dowel-registered nodular iron four-bolt main caps secured with 1/2-inch bolts, a priority main oiling system, and thicker cylinder walls. This block also features expanded water passages to allow improved cooling for big displacement. To learn more visit www.theengineshop.com.

Any block should be checked for proper specification before assembly begins. Here the main bearing clearances are being checked with a dial-bore gauge.

On this small-block Chevy, the upper half of the main bearing is placed into the block. Note that the upper is grooved and has a hole for lubricating. The lower half of the bearing fits in the main cap and has neither groove nor hole.

These dark areas at the front side of the rear main bearing are oil pockets that supply oil to the thrust surface of the crankshaft.

Four-bolt main caps are generally mandatory for engines used in moderate to serious competition. If you have a two-bolt main block, chances are very good that it will work just fine for most street performance applications up to 375/400 horsepower level.

This photo shows two things: the approximate thickness of a cylinder wall in a production small-block Chevy and what can happen to a cylinder bore if the crankshaft throws a connecting rod!

True, the first passenger car equipped with the legendary small-block Chevy was the '55 Chevy with its 265-cubic-inch small-block. But did you know that the first Chevrolet produced with an overhead valve V-8 occurred in 1917? Yes, the Chevrolet Series D had a 288-cubic-inch overhead valve V-8 that pumped out a whopping 55 horses. Chevrolet sold just over 2,800 of these cars almost 90 years ago.

This is the bottom of GM's '04 Vortec 3500 I5 (in-line five-cylinder) engine block. The block is cast from aluminum and the main caps are arranged as an assembly.

The new Chevrolet LS2 (available in the '05 Corvette and a version of the SSR) displaces 364 cubic inches (6.0L) and makes 400 horsepower at 6,000 rpm. All of this is based on an all-new 319-T5 aluminum deep-skirt block casting with cast-in-place iron cylinder bore liners and cross-bolted main caps to ensure rigidity.

Cadillac is experimenting with this new V-16 engine. This block is cast from aluminum and uses all of today's latest technology. One fundamental reason that Cadillac is pursuing this V-16 engine is to differentiate itself from all the other high-priced cars, just as it did with the Cadillac V-16s of the 1930s.

This aluminum Vortec 2800 I4 block casting (left) is manufactured from adding a lost-foam model (right) into a mold.

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