🔍 Key Concepts

• Identify where the rocker arms are located in the cylinder head in the illustration and trace what each end of the rocker arm touches. • Recall the basic function of a rocker arm in a four-stroke diesel: it is moved by the cam/follower and pushes on something else. • Consider which engine components in the drawing control valve opening and which control fuel injection or starting air.

💭 Think About

• In the illustration, follow the motion path: cam → push rod (or cam follower) → rocker arm → ? What does the far end of the rocker arm act on? • Which of the labeled components in the cylinder head are intake valves, exhaust valves, starting valves, and fuel injectors? Do the rocker arms contact all of them or only some? • Ask yourself: does a rocker arm usually convert rotation directly to pressure, or does it mainly transfer motion between two reciprocating parts?

✅ Before You Answer

• Verify which valves (intake, exhaust, or starting) have rocker tips pressing on their stems in the picture. • Check whether the fuel injector or unit injector is operated by a separate rocker or linkage, or by the same rocker as the exhaust valve. • Confirm that the rocker arm’s job is to transfer cam motion rather than to be the primary device converting rotational to reciprocating motion.