COMPONENTS OF ENGINE

ENGINE BLOCK

Learning Objective:

Given a description of engine block functions, identify the engine block part described

The engine block is the main part of the engine; all parts of the engine are either inside the engine block or attached to the outside of it. The engine block is one-piece casting of iron, but actually it is considered in two parts, the crankcase and the cylinder block.

1. Crankcase

To illustrate the two parts of the engine block, an imaginary box has been drawn around the lower portion of the engine block. This lower portion is known as the crankcase. 

Four-cylinder engine block (left rear view)

The crankcase which support the crankshaft, is hallow inside with one or more rib-like castings that form the mainframe.

Eight Cylinder Engine Block

2. Cylinder Block The upper portion of the engine block is the cylinder block. This portion contains the cylinders, the water passages commonly known as water jacket and oil passages.

Engine Block Coolant Flow

Oil Passages

The cylinders are the individual housing for the pistons. They are large holes cast into the cylinder block, extending completely through it. The walls of the cylinders are machined smooth to reduce the friction generated by the moving parts inside them. Some engines have cylinder liners inserted into the cylinder opening.

The water jacket, a large passage cast into cylinder block, surrounds the cylinder. It contains water or commercial coolant to maintain safe temperature while the engine is operating.

Note the oil passage provide a way to distribute oil under pressure to all moving parts of the engine to reduce wear and aid the water jacket in cooling the moving parts.

Cylinder block (top view of cylinders and water passages).