What is an engine block?

The engine block is an engine component that performs several functions. In a sense, it's the backbone of a piston engine. Understanding it will help us understand what's under the hood and how our vehicle works.

What's the purpose of the engine block?

The engine block is directly connected to the cylinder head through the cylinder head gasket. It is the structure on which the rest of the components are placed, such as the cylinder on top, the pistons inside, and the base on the bottom. The engine block is most often made of aluminum to ensure high strength. It must be able to withstand high temperatures, friction, and exhaust pressure. For this reason, the engine block has perfect thermal conductivity and light mass.

The main function of the engine block is to turn the crankshaft through the rotation of the pistons, but it also serves to:

• Guide the pistons;
• Support the crankshaft;
• Maintain cylinder tightness;
• Allow cooling and engine oil circuits to pass through.

The different types of engine block

This part is divided into two main categories: linerless engine blocks and engine blocks with liners (dry or wet liners).

Linerless engine block

In this type of engine block, the cylinders are cast directly into a single piece of cast iron. In this case, the block and cylinders are combined in a single piece. It's also called a direct bore block. When the cylinders wear out, they must be rebored to a larger size, and then larger diameter pistons must be installed.

Block with liners

To minimize wear on the cylinder walls, some manufacturers equip their vehicles with engine blocks with liners. These liners are very strong. They are installed in the cylinder bores.

The liner is a tube that can be removed from the cylinder. Before being installed, it is made of a material (cast iron or steel) that is stronger than the cylinder block. To ensure optimum strength, this component is centrifugally cast in suitable plants. This type of block can be fitted with either dry or wet liners.

Blocks with dry liners

Blocks with dry liners are made of aluminum or cast iron. In the case of aluminum blocks, the dry liners are installed when the block is manufactured. As a result, they are sometimes not replaceable but can be rebored. On some models, the liners can be replaced because they are shrink-fitted. On a cast iron block, it's perfectly possible to replace the liners if they are badly worn.

But whether the block is cast iron or aluminum, there must be fins or water chambers to cool the engine.

Blocks with wet liners

In this type of block, the liners are housed in a hollow crankcase. The upper section is supported by the cylinder head, while the lower section is supported by the crankcase.

The liners are easier to replace. On 1920s liquid-cooled engines with wet steel liners in an aluminum block, liner removal can be particularly difficult. This makes liner replacement much more difficult.

Engine block materials

Engine blocks are generally made of cast iron or aluminum. The former provides greater strength for the same volume, and the latter saves weight and improves cooling.

The general trend is toward aluminum for several reasons. For example, better design and construction quality allow aluminum engine blocks to provide very high strength. Also, the advantages of this material are highly desirable for today's prevailing reduction of emissions (weight reduction).

Concerning its conductivity. Aluminum blocks have a lower thermal inertia. This means that they take less time to heat up and less time to cool down. This, combined with a well-designed cooling system and block, allows the entire engine to reach operating temperature faster and dissipate heat more efficiently when needed.

Because cast iron blocks take longer to heat up, they require secondary coolant passages. This allows the heat to be distributed evenly throughout the block from the start, avoiding damaging temperature differences.

In addition, a lighter aluminum engine makes it easier to achieve a better front-to-rear weight balance. This, in turn, can improve vehicle dynamics.

How much does an engine block cost?

An engine block is generally quite expensive. The price of an engine block depends on the make, model, and engine. The lowest prices start at around $500 for an engine block and can exceed $1,000.

If you hire a professional to clean your engine block, you must also factor in the cost of labor. This will be even higher if the engine block needs to be disassembled.