Torque Specifications for a 3406 Cat Engine

by Anne Davis
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The Caterpillar 3406 engine has regular scheduled maintenance you must perform in order to keep it in proper working order. Much of this maintenance requiring specific applications of torque, such as removing the injector, should occur at 100,000 miles or 2,000 service hours. The Caterpillar engines' classifications are 3406, 3406B, 3406C or 3406E. Each engine has a unique purpose and unique maintenance requirements.

Horsepower and Torque

Depending on its specifications, the 3406 engine can produce anywhere between 250 horsepower at 1,600 rpm and 550 horsepower at 2,100 rpm. It can produce between 1,000 pound-feet of torque at 1,200 rpm and 1,850 pound-feet of torque at 1,200 rpm. In this context, torque refers to the total amount of work that the 3406 engine can do, while horsepower is a rate-based measurement of how quickly the engine can perform that work.

Bridge Adjustment Torque

Every 100,000 miles or 2,000 service hours, your 3406 engine will require a bridge adjustment. This maintenance should happen only after the valves have been ground or any other reconditioning of the cylinder head is complete. After completing the necessary steps, you should hold the adjusting screw in its position and tighten the component's locknut to 22 foot-pounds of torque.

Injector Torque

When removing, cleaning and re-installing the fuel injector, which should occur every 100,000 miles or 2,000 service hours, you should tighten the retainer nuts to 55 foot-pounds of torque. Over- or under-torquing these nuts could result in fuel nozzle or engine failure.


You can identify your engine and its specific requirements by its serial number. These numbers denote the engine's size and specific details. For example, a 2EK serial number indicates that the engine is a 3406B engine, and a 5KJ serial number indicates a 3406C engine. Verify your engine's serial numbers with your maintenance manual to ensure that the torque specifications you follow are correct for your engine.

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