Engine Classification

There are two major classifications of engines: the internal and the external combustion engines. The engine that burns fuel inside its combustion chamber is called the internal combustion engine, while the engine that burns its fuel outside is called external combustion engine.

All automobile engines are of the internal combustion type, and they are also classified as follows:

According to Cylinder Arrangement

1. Vertical In-line. This is the simplest form of cylinder arrangements. The cylinders are arranged in-line in a vertical position.

2. Slanted In-line. The cylinders are still in-line but slightly slanted to one side. This car body style requires a lower engine hood. This slanted in-line design is made for stability.

3. V-Type. The main advantage of the V-type over the in-line is that the form is shorter and, therefore, needs a smaller engine room.

4. Horizontally Opposed. This engine has its cylinders arranged in two flat banks with the crankshaft between them. It provides a better mechanical balance and suited to the car with very limited space.

According to Valve Arrangement

The development of high-performance engines led to the variations in valve arrangements. The early mobile which were of the low compression designs were the F-type and L-type. Nowadays, most engines have their valves in the cylinder head, and modifications in the camshaft mountings have been introduced.

The intake and exhaust valves can be arranged in various ways in the engine cylinder head or block.

a. I-head Engine. In the I-head or overhead valve engine, the valves are in the cylinder head. In inline engines, the valves are usually in a single row.

b. V-8 Engines, I Head. The valves may be in a single row in each bank or in a double row in each bank. Either way, single camshaft operates all valves. The valve lifters, push rods, and rocker arms carry the motion from the cams to the valves.

c. L-Head Engine. In the L-head arrangement, the combustion chamber and the cylinder form an inverted L. The intake and exhaust valves are located side by side. All the valves for the engines are set in one line (except that V-8 L-head engines are in two lines). This way, a single camshaft can be used to operate all valves.)

d. V-8 Engines, L-Head. The intake and exhaust valves are arranged in two lines in the cylinder block.

e. Overhead camshafts. The I-head engine used push rods and rocket arms to operate the valves. This design is often called a push-rod engine. The push rods and rocker arms impose some inertia that affet valve action. The push rods and rocker arms flex or base slightly before they open the valve.

f. F-Head Engines. The intake valve are in a single row in the cylinder head while the exhaust are arranged in one row in the cylinder block.