When adjusting the valve clearances on the engine, Technician A says the valves are closed when the valve lifter or follower is on the inner base circle of the camshaft lobe. Technician B says that valves are always adjusted when closed while the lifter or follower is on the camshaft lobe nose. Who is correct?

A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B

The correct option is (A) technician A only.

Nose- Lobe nose is the top part of the lobe. at this point, the valve is kept open for TDC to BDC transitions.

This is the point where the valve is held open as it transitions from opening to closing.

Statement A- Valves are closed when the valve lifter or follower is on the inner base circle of the camshaft lobe.

According to the base circle definition, the valve lifter/follower should be on the inner base circle of the camshaft lobe. Therefore the statement of technician A is correct.

Statement B- Valves are always adjusted when closed while the lifter or follower is on the camshaft lobe nose.

By the definition of the nose, we can say that the statement of technician B is incorrect.

Hence, the correct option is (A) technician A only,

For more about the camshaft follow the link,

link

A. Technician A only

Explanation:

The camshaft opening ramp is what opens the valve, it starts at the basement of the inner circle and closes at the nose while the camshaft closing ramp allows for closing a valve starts at the nose and closes at the inner base circle. Valve clearance on an engine are performed when closing a valve, and is completed when the valve lifter or follower is on the inner base circle of the camshaft lobe.