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In an internal combustion engine, the engine block is the structure that contains the cylinders and other components. The engine block in an early automotive engine consisted of just the cylinder block, to which a separate crankcase was attached. Modern engine blocks typically have the crankcase integrated with the cylinder block as a single component. Engine blocks often also include elements such as coolant passages and Motor oil galleries.
The term "cylinder block" is often used interchangeably with "engine block". However, technically, the block of a modern engine (i.e., multiple cylinders integrated with another component) would be classified as a monobloc engine.
The evolution from separate components to monobloc engine blocks has gradually progressed since the early 20th century. The integration of elements has relied on the development of foundry and machining techniques. For example, a practical, low-cost V8 engine was not feasible until Ford developed the methods used to build its flathead V8 engine. Other manufacturers then applied those techniques to their engines.
In early engines with multiple cylinder bankssuch as V6, V8, or Flat-six engine engineseach bank was typically made of one or multiple separate cylinder blocks. Since the 1930s, mass production methods have developed to allow both banks of cylinders to be integrated into the same cylinder block.
The advantages of wet liners are a lower mass, reduced space requirements, and coolant being heated faster from a cold start, reducing start-up fuel consumption and heating the car cabin sooner.
Dry liner cylinder blocks use either the block's material or a discrete liner inserted into the block to form the backbone of the cylinder wall. Additional sleeves are inserted within, which remain "dry" outside, surrounded by the block's material.
For either wet or dry liner designs, the liners (or sleeves) can be replaced, potentially allowing an engine overhaul or rebuild without replacing the block itself. However, there are more practical repair options.
Weight reductions through material selection. Presently, most of the engine blocks in mass production are gray castings. Reducing weight has resulted in using aluminum-silicon alloys more frequently for the engine block in small-displacement engines. Engine blocks of comparable design, but using Al-Si alloys, are not lighter than cast iron engine blocks in the same ratio as that for the specific weights of the materials.
In engine blocks made of gray cast iron, weight can be reduced by optimizing the structure and thin-wall casting. With this casting technique, a wall thickness of as little as about 3 mm is generally possible. In comparison, the walls of cast iron engine blocks are usually from 4.0 to 5.5 mm thick.
Using vermicular graphite cast iron (GGV), a casting material with great strength, enables weight reductions by about 30% compared to conventional casting materials such as GG 25. Weight reduction, to this extent, requires engineering for the engine block, taking into account the particular needs of the material.
In the early years of the internal combustion engine, casting technology couldn't produce large castings with complex internal cores (for etc). Most early engines, particularly those with more than four cylinders, had their cylinders cast as pairs or triplets of cylinders, then bolted to a separate crankcase.
As casting techniques improved, an entire cylinder block of 4, 6, or 8 cylinders could be produced in one piece. This monobloc construction was more straightforward and more cost-effective to produce. All the cylinders and crankcase could be made in a single component for straight engine cylinder layouts. One of the early engines produced using this method is the 4-cylinder engine in the Ford Model T, introduced in 1908. The technique spread to straight-six engines and was commonly used by the mid-1920s.
Up until the 1930s, most retained a separate block casting for each cylinder bank, with both bolted onto a common crankcase (itself a separate casting). For economy, some engines were designed to use identical castings for each bank, left and right. A rare exception was the Lancia 22½° narrow-angle V12 of 1919, which used a single block casting combining both banks. The Ford flathead V8introduced in 1932represented a significant development in the production of affordable V engines. It was the first V8 engine with a single-engine block casting, putting a V8 into an affordable car for the first time. (2025). 9780814332795, Norton. ISBN 9780814332795
The communal water jacket of monobloc designs permitted closer spacing between cylinders. The monobloc design approach also improved engines' Stiffness as cylinder numbers, engine lengths, and power ratings increased.
Using steel cylinder liners and Main bearing shells minimizes the effect of the relative softness of aluminium. Some engine designs use plasma transferred wire arc thermal spraying, instead of cylinder sleeves, to further reduce weight. These types of engines can also be made of compacted graphite iron, such as in some diesel engines.
An example of engines with integrated cylinder heads are the Honda GC-series and GXV-series engines, which are sometimes called "Uniblock" by Honda. Includes sectioned drawings
Motorcycles such as the Honda CB750 use a similar layout, with the cylinder block and crankcase integrated with part of the transmission.
Many farm tractor designs integrate the cylinder block, crankcase, transmission, and rear axle into a single unit. An early example is the Fordson tractor.
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