C7.1 Industrial Engine Basic Engine Caterpillar

Basic Engine
C7.1 Industrial Engine [KENR9104]
1.1. Introduction
2.1. Cylinder Block
3.1. Cylinder Head
4.1. Pistons, Rings, and Connecting rods
5.1. Crankshaft
6.1. Vibration Damper
7.1. Gears and Timing Gear Case
8.1. Camshaft


The eight major mechanical components of the basic engine are the following parts:

  • Cylinder block

  • Cylinder head

  • Pistons

  • Connecting rods

  • Crankshaft

  • Vibration damper

  • Timing gear case and gears

  • Camshaft

Cylinder Block

Illustration 1g01907673
Typical example

The cast iron cylinder block for the C7.1 engine has six cylinders which are arranged in-line. The cylinder block is made of cast iron. The cylinder block provides support for the full length of the cylinder bores. The cylinder bores are machined into the block.

The cylinders are honed to a specially controlled finish in order to ensure long life and low oil consumption.

The cylinder block has seven main bearings which support the crankshaft. Thrust washers are installed on both sides of number 6 main bearing in order to control the end play of the crankshaft. The thrust washers can only be installed one way.

Passages supply the lubrication for the crankshaft bearings. These passages are machined into the cylinder block.

Cooling passages are cast into the cylinder block in order to allow the circulation of coolant.

The cylinder block has a bush that is installed for the front camshaft journal. The other camshaft journals run directly in the cylinder block.

The engine has a cooling jet that is installed in the cylinder block for each cylinder. The piston cooling jet sprays lubricating oil onto the inner surface of the piston in order to cool the piston.

A Multi-Layered Steel (MLS) cylinder head gasket is used between the engine block and the cylinder head in order to seal combustion gases, water, and oil.

Cylinder Head

Illustration 2g02212800
Typical example
(1) Valve keepers
(2) Valve spring retainer
(3) Valve spring

The engine has a cast iron cylinder head (5). The inlet manifold is integral within the cylinder head. There are two inlet valves and two exhaust valves for each cylinder. Each pair of valves (6) are connected by a valve bridge that is controlled by a pushrod valve system. The ports for the inlet valves are on the left side of the cylinder head. The ports for the exhaust valves are on the right side of the cylinder head. The valve stems move in valve guides that are pressed into the cylinder head. There is a renewable stem seal (4) that fits over the top of the valve guide. The valve seats are replaceable.

Pistons, Rings, and Connecting rods

Illustration 3g02394336
Typical example

The pistons (9) have a Quiescent combustion chamber in the top of the piston in order to provide an efficient mix of fuel and air. The piston pin (8) is off-center in order to reduce the noise level. The position pin (8) is retained in the correct position by two circlips (3).

The pistons have two compression rings (1) and an oil control ring (2). The groove for the top ring has a hard metal insert in order to reduce wear of the groove. The piston skirt has a coating of graphite in order to reduce the risk of seizure when the engine is new to reduce friction and improve fuel economy.

The correct piston height is important in order to ensure that the piston does not contact the cylinder head. The correct piston height also ensures the efficient combustion of fuel which is necessary in order to conform to requirements for emissions.

The connecting rods (4) are machined from forged steel. The connecting rods have bearing caps (6) that are fracture split. Two connecting rod bearings (5) are installed between the connecting rod (4) and the bearing cap (6). The bearing caps on fracture split connecting rods are retained with Torx bolts (7). Connecting rods with bearing caps that are fracture split have the following characteristics:

  • The splitting produces an accurately matched surface on each side of the fracture for improved strength.

  • The correct connecting rod must be installed with the correct bearing cap. Each connecting rod and bearing cap have an unique serial number. When a connecting rod is assembled the serial numbers for the connecting rod and bearing cap must match.


Illustration 4g01907674
Typical example
(1) Crankshaft gear
(2) Crankshaft
(3) Crankshaft thrust washers
(4) Crankshaft timing ring

The crankshaft is a chromium molybdenum steel forging. The crankshaft has seven main journals. Thrust washers are installed on both sides of number six main bearing in order to control the end play of the crankshaft.

The crankshaft changes the linear energy of the pistons and connecting rods into rotary torque in order to power external equipment.

A gear at the front of the crankshaft drives the timing gears. The crankshaft gear turns the idler gear which then turns the following gears:

  • Camshaft gear

  • Fuel injection pump and fuel transfer pump

  • The idler gear is driven by the crankshaft gear which turns the gear of the lubricating oil pump.

Lip type seals are used on both the front of the crankshaft and the rear of the crankshaft.

A timing ring is installed to the crankshaft. The timing ring is used by the ECM in order to measure the engine speed and the engine position.

Vibration Damper

Illustration 5g02153930
Typical example
(1) Setscrews
(2) Setscrews
(3) Vibration damper
(4) Crankshaft pulley
(5) Crankshaft adapter

The force from combustion in the cylinders will cause the crankshaft to twist. This is called torsional vibration. If the vibration is too great, the crankshaft will be damaged. The vibration damper is filled with viscous fluid in order to limit the torsional vibration.

Gears and Timing Gear Case

Illustration 6g02212814
Typical example
(1) Hole for the water pump gear
(3) Position of the accessory drive gear

The crankshaft oil seal is mounted in the cover of the timing case. The timing case cover is made from sound-deadened steel or cast iron.

The timing gears are made of steel.

The crankshaft gear (5) drives an upper idler gear (4) and a lower idler gear. The upper idler gear (4) drives the camshaft gear (6) and the fuel injection pump gear (2). The lower idler gear drives the oil pump. The water pump drive gear is driven by the fuel injection pump gear.

The camshaft rotates at half the engine speed. The fuel injection pump rotates at engine speed.


The engine has a single camshaft. The camshaft is made of cast iron. The camshaft lobes are chill hardened.

The camshaft is driven at the front end. As the camshaft turns, the camshaft lobes move the valve system components. The valve system components move the cylinder valves.

The camshaft gear must be timed to the crankshaft gear. The relationship between the lobes and the camshaft gear causes the valves in each cylinder to open at the correct time. The relationship between the lobes and the camshaft gear also causes the valves in each cylinder to close at the correct time.