Engine Terms & Definitions

Long Block Assembly
The long block assembly is essentially the "engine" alone. When a long block is delivered it will not include the attachments that are needed to make it run. For example, the fuel injection system, the alternator, power steering pump and other items attached to the long block will have to be installed. It will include the head or heads.

Short Block
The short block is just the lower part of the engine. It however does not include the cylinder head or heads. It will need cylinder heads installed to make it run. It also does not have any outside attachments like the long block assembly. It does not include the head or heads.

Cylinder Head
The cylinder head is the top part of the engine that mounts to the short block or lower end of the engine. It contains the valves, and in the case of the over head cam engine, the cam shaft. This is where the fuel injection and the exhaust bolt to the engine, the exhaust and intake ports.

Cam Shaft
This is the part of the motor that controls the valves. It is designed to open and close them at a specific time and for a specific amount. It is connected in most cases to the crankshaft by a timing belt, or timing chain.

Timing Belt
This is a rubber and fiber belt similar to a fan belt that is connected to the crankshaft and the camshaft. As the crankshft turns, it turns the camshaft that opens and closes the valves.

Crankshaft
This is the part of the engine that takes the up and down motion of the pistons in the cylinders and converts it to a rotating motion that then turns the transmission. The crankshaft rides in a cradle. The space between the crankshaft and the cradle contains a main bearing. This allows a thin layer of oil to lubricate and cool the two surfaces and prevents them from damaging each other.

Cylinder
The cylinder contains the piston and the combustion area where the fuel and air are mixed. The piston is connected to the crankshaft by a connecting rod.

Connecting Rod
The connecting rod is connected to the piston and the crankshaft. It rides with the piston in the up and down motion. Between the connecting rod and the crankshaft is the rod bearing.

Rod Bearing
The rod bearing is a piece of metal that sits between the rod and crankshaft. This allows a thin layer of oil to lubricate and cool the surfaces to keep them from damaging each other.

Piston
The piston is connected to the rod. The piston rides up and down in the cylinder. It is slightly smaller in diameter than the cylinder. Mounted on the piston are the piston rings that take up the space between the piston and cylinder.

Piston Rings
The piston rings bridge the gap between the piston and the cylinder. They are what hold the fuel and air mixture and compress it as the piston moves to the top of the cylinder. In most cases there are three rings. Two of the rings hold the compressed fuel and air. One of the rings, the oil ring or oil wiper ring, picks up oil and lubricates the cylinder.

Exhaust Port
The exhaust port is where the exhaust is ejected from the engine after the combustion in the cylinder.

Intake Port
This is the passage where the fuel and air mixture is delivered to the cylinder.

The Oil Pan
This is where the oil is stored and where the iol is picked up by the oil pump to send it throughout the engine.

Front & Rear Crankshaft Seals and Camshaft Seals
The seals keep the oil in the engine.

Overhead Cam
The term, overhead cam or ohc, describes the position of the cam relative to the head. Its over the head or on top of the head. The cam or cams ride in a cradle and are connected to the valves by cam followers or lifters. These parts ride up and down on the lobes of the cam and push the valve down to open them . The valve springs close the valves.

Dual Overhead Cam or DOHC
This refers to two cams over the head. One cam operates the intake valves, one operates the exhaust valve. Both are connected to the crankshaft by a timing belt or chain.

Litres or CC's
This refers to the capacity of the combustion chambers measured in a liquid measurement.

Cubic inch or Cu I
The same as "cc" but measured in cubic inches.