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Head Bolt Torque Specifications for the 5.9 Cummins

by David Marsh

In 1989, the Cummins 5.9 Diesel engine became the first medium-duty diesel engine put in a light-duty truck sold to the general public. The engine had been used only in commercial trucks before that time. Dodge provided the engine in its Ram pickups for drivers who hauled heavy loads long distances.

Torque

When a homeowner tightens a screw inside a door frame, he's applying torque to the screw. Torque is twisting force. It's measured with a special wrench, called a torque wrench, equipped with a dial showing the amount of twisting force being applied. Sometimes the torque wrench will have a system of cams and springs that can be set to release at a pre-set torque value.

The Cylinder Head

The cylinder head sits between the intake manifold and the engine block. It forms the upper part of the combustion chamber and holds the valves to let the fuel/air mixture into the combustion chamber and the exhaust gas out. It also has tunnels, called ports, through which the fuel/air mixture and the exhaust gases travel on their way into and out of the combustion chamber. The cylinder head bolts to the engine block. The bolts must be tightened with a certain amount of force. Too much force and the bolts weaken or the threads on each bolt are damaged. Too little and there will be leaks of coolant or vacuum.

Cylinder Head Torque Settings

For the Cummins 5.9-liter engines made between 1983 and 1989, the bolts in the cylinder head must be tightened to 89 foot-pounds plus an extra 1/4 turn. For engines made between 1998 and 2003, the figure is 77 foot-pounds plus the extra 1/4 turn. The bolts must be tightened in a certain pattern and to intermediate torque settings, which are usually finger tight, half of the final figure and full torque. The owner's manual has a diagram and the intermediate settings.

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