Cylinder block

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The cylinder block of a Ford I4 DOHC engine
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The cylinder block of a Ford I4 DOHC engine

The cylinder block or engine block is a machined casting (or sometimes an assembly of modules) containing cylindrically bored holes for the pistons of a multi-cylinder reciprocating internal combustion engine, or for a similarly constructed device such as a pump. It is a complicated part at the heart of an engine, with adaptions to attach the cylinder head, crankcase, engine mounts, drive housing and engine ancillaries, with passages for coolants and lubricants. The distance between the cylinder bores (midpoint to midpoint) cannot easily be changed since the machining facilities would require extensive modification. Instead, the bore diameter is commonly varied to obtain different engine displacements. This and the minimum thickness of material required between two cylinders are a limiting factor concerning the potential displacement because the bore to stroke ratio has to stay within certain limits. They are made out of cast metal.

The size of the distance between the cylinder bores has led to a distinction between the V8 engine families the Detroit Big Three automakers (Ford, GM and DC) have been building since the 1950s: There are Small-block and Big-block engines. These families differ in respect to the distance between cylinder bores, but not necessarily in displacement since the latter is defined by bore and stroke.

Whilst the big-blocks have been less commonly used in recent years, the small-block families have grown in displacement and have now reached a level that was reserved for big-blocks in previous years (up to 7 litres of displacement in a Corvette). Even though the technology has greatly changed, basic specifications have been the same for fifty years[1].

Contents

[edit] Big block

A big-block Oldsmobile 400 cubic engine, which is capable of delivering 360 horsepower and 440 foot-lbs of torque.
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A big-block Oldsmobile 400 cubic engine, which is capable of delivering 360 horsepower and 440 foot-lbs of torque.

A big-block engine is a North American V8 in a family of engines which generally have greater than 5.9 L (360 cubic inches) of displacement; factory engine sizes reached a peak of 8.2 L (500 cubic inches) in Cadillac's 1970s range. Since then manufacturers have responded to the need for superior engines, as well as the need to replace surviving worn-out, decades-old big-block racing engines which have been rebuilt too many times. In 2002 General Motors released the carbureted Chevrolet 572 crate engine (9.4L), available for installation in most vehicles which have enough room under the hood, both in a 620 hp street version, which runs on premium gasoline, and a 720 hp version, which requires racing fuel. Mopar (Chrysler) recently released the 528 Hemi (8.7L) and 540 (8.8L) crate engines. Both of these incorporate modern hardened metals and are able to run on unleaded gasoline.

Smaller V8 engines are known as small-blocks; some members of small-block engine families may exceed 6 L, blurring the distinction somewhat. The distinction came about in the early 1960s when the large full-size cars needed a bigger V8 than the smaller mid-size and compact cars. Before that, manufacturers normally had only one V8 engine line.

The term is normally used only for engines from the "Big Three" (Ford Motor Company, General Motors, and Chrysler Corporation) since the other companies did not keep two V8 engine size families.

Big-block V8s were most commonly used in full-size and luxury cars, rather than performance vehicles. Thus, they were commonly tuned and built for smooth, low-end torque to get heavy cars rolling and effortlessly cruising. Many big-block engines were less technically sophisticated than their small-block counterparts, and their power-to-weight ratios were often lower. Today of course big-block engines are used in racing.

However, they did see performance applications. Performance-tuned big-blocks were used in NASCAR racing, and homologation requirements saw these engines sold for road use. Because of NASCAR's 7 L engine size limit, many high-performance big-block engines, like the Chevrolet's 427, Ford's 427, and Chrysler's 426 Hemi engines, were built to this size. In the mid to late 1960s, the explosion of the muscle car market saw performance big-blocks fitted to intermediate-size cars. Some used derivatives of the racing engines, but in addition performance versions of former luxury motors were produced.

After the 1973 oil crisis, the days of the big-block in passenger cars were numbered. By the end of the 1970s, they were no longer to be found. However, these engines remained in use in pickup trucks and other non-car uses. Currently, only GM offers big-block V8s in its trucks; Ford and Chrysler essentially replaced their big-blocks with stretched V10 versions of their small-block engines in the early to mid 1990s.

[edit] Ford

Ford does not categorize its engines using the big/small block nomenclature. Rather, Ford literature distinguishes engine by its series, or family. Enthusiasts unaware of this fine point will nonetheless classify the larger families as big block engines. Third-party equipment vendors, following suit, have adopted the practice as well.[1]

  • Ford FE series - this family includes engines as small as 332 ci.
  • Ford 385 series - successor to the FE family
  • Ford 335 series - also erroneously referred to as "mid block", because its larger displacement engines will mate with bellhousings shared by smaller displacement families.

[edit] General Motors

[edit] Chrysler

[edit] Small-block

A small-block engine is a North American V8 in a family of engines which generally have less than 6 liters (360 in³) of displacement, although some derivatives have grown larger (up to 427 in³, 7.0 L). A 505in³, 8.3 L V10 is produced by Chrysler, a derivative of the LA engines. Larger families of engines are called big-blocks. The distinction came about in the late 1950s when the large full-size cars needed a bigger V8 than the smaller mid-size and compact cars - though consumers wanted a V8 under the hood, the recession of the late 1950s provided some of the earliest American awareness of fuel economy. Prior to that point, manufacturers normally had only one V8 engine line.

The term is normally used only for engines from the "Big Three" (Ford Motor Company, General Motors, and Chrysler Corporation) since the other companies did not keep two V8 engine size families. However, it is sometimes used for the more modern and compact V8s produced by others, such as Studebaker.

The term "block" refers to a piston engine cylinder block, which is the lower portion of a piston engine containing the pistons and cylinder bores.

Although a small-block V8 generally has a smaller displacement than the equivalent big-block, a small-block engine can be built to develop significant amounts of power. Additionally, many small-block engines were more advanced technologically than their big-block counterparts, and were much lighter and smaller. Innovations such as aluminum heads and blocks generally came first to small-blocks. From a new car buyer's standpoint, they tended to offer an acceptable compromise between horsepower and economy, so they were a popular option instead of the basic I6 or V6 engine base model. Because of their attractive combination of popularity (and therefore low-cost availability) coupled with good performance, good fuel economy and light weight, they were often preferred in racing and sporting applications. Many hot rods and custom cars are fitted with small-block V8s, particularly the GM (Chevrolet) 350 engine and the Ford 351 Windsor.

There are some cases in which small-blocks seem to encroach upon big-block displacements; in these cases it is most important to keep in mind that small-block and big-block refer to engine families, not simply displacements. For example, engines ranging from the 4.8 L Vortec 4800 to the 7.0 L LS7 are all GM small block V8s, and share the same general external dimensions. The LS7 achieves enormous displacement by having a very large bore and stroke in the same compact block as previous small-blocks, but has very little space between cylinders. This would not be acceptable in a truck engine, and was not possible forty years ago. As a result, 7.0 L is a displacement ordinarily reserved for big-blocks, which can achieve it with fewer compromises in reliability and less engineering effort. A 7.0 L big block, like the 427 Chevy first seen in 1966 Corvettes, is a much larger engine externally and shares external dimesions with engines ranging from the 6.5 L 396 to the 8.1 L Vortec 8100.

[edit] Ford

Ford does not categorize its engines using the big/small block nomenclature. Rather, Ford literature distinguishes engine by its series, or family. Enthusiasts unaware of this fine point will nonetheless classify the smaller families as small block engines. Third-party equipment vendors, following suit, have taken up the practice as well.[2]

[edit] GM

General Motors small-block V8s include:

[edit] Chrysler

Chrysler Corporation small-blocks include:

[edit] See also

[edit] References

  1. ^ Motortrend
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