Question 1

Technician ​A says that camshaft end thrust on a pushrod engine with a camshaft-driven oil pump results from resistance of oil being pumped by the oil pump. Technician B says that flat tappet camshafts are usually inspected by visually checking the wear pattern on the lobes for edge loading. Who is right?

Accepted Answer

Technician A is correct because the resistance encountered by the oil pump, which is driven by the camshaft, can indeed create end thrust on the camshaft in a pushrod engine. Technician B is also correct because inspecting flat tappet camshafts typically involves visually checking the wear patterns on the lobes to identify issues like edge loading, which can indicate improper contact and wear.

Question 2

Two technicians are discussing flat tappet camshafts. Technician A says that a valve lifter must be perfectly centered above its corresponding cam lobe. Technician B says a pushrod engine cam lobe is slightly tapered across its face. Who is right?

Accepted Answer

A valve lifter must be perfectly centered above its corresponding cam lobe, and a pushrod engine cam lobe is slightly tapered across its face.

Question 3

The exhaust valves shown in the preceding photograph are from a four cylinder interference engine that has failed. All of the valves are bent an equal amount. Which of the following could be the cause?

Accepted Answer

Both a broken timing belt and excessive chain slack can lead to a situation where the timing between the piston and valve movement is lost, causing the valves to collide with the pistons in an interference engine, resulting in bent valves.

Question 4

The cam lobes in the photograph shown here are for the number one cylinder and its companion on an in-line pushrod engine that rotates counterclockwise when viewed from the rear. The lobes are positioned:

Accepted Answer

The answer of The cam lobes in the photograph shown...

Question 5

Technician A says that it is necessary to keep flat tappets in order if the old cam and lifters are to be used again. Technician B says that used roller tappets should not be installed on a new camshaft. Who is right?

Accepted Answer

Technician A is correct, as flat tappets can develop a wear pattern on the old camshaft that is matched to their shape. Therefore, they should be kept in order and returned to their original location if being reused with the old camshaft. 
Technician B is also correct, as used roller tappets can develop a wear pattern on the old camshaft that is matched to their shape. Therefore, it is recommended that new roller tappets be installed with a new camshaft to ensure proper wear and function.

Quiz 9: Camshafts, Lifters, Timing Belts, and Chains

Two technicians are discussing flat tappet camshafts. Technician A says that a valve lifter must be perfectly centered above its corresponding cam lobe. Technician B says a pushrod engine cam lobe is slightly tapered across its face. Who is right?

The exhaust valves shown in the preceding photograph are from a four cylinder interference engine that has failed. All of the valves are bent an equal amount. Which of the following could be the cause?

The cam lobes in the photograph shown here are for the number one cylinder and its companion on an in-line pushrod engine that rotates counterclockwise when viewed from the rear. The lobes are positioned:

Technician A says that it is necessary to keep flat tappets in order if the old cam and lifters are to be used again. Technician B says that used roller tappets should not be installed on a new camshaft. Who is right?