Cam Lobe
An eccentric projection on a camshaft that pushes against valves or lifters to open and close the engine valves.
A cam lobe is an egg-shaped projection on the camshaft. As the camshaft rotates, the lobe's eccentric shape pushes down on the valve lifter, pushrod, or rocker arm, which in turn opens the intake or exhaust valves. The shape and height of the cam lobe determine how far the valve opens (lift) and how long it stays open (duration).
Cam lobes must withstand extreme friction as they slide against lifters or rocker arms, relying on a constant film of engine oil. If the engine suffers from oil starvation, dirty oil, or if the wrong oil viscosity is used, the cam lobes can wear down or become flat (known as a wiped lobe).
A worn cam lobe will fail to open its corresponding valve fully, severely restricting airflow into or out of that cylinder. This leads to engine misfires, a tick or tapping noise, a significant loss of engine power, and poor fuel economy, requiring replacement of the camshaft.