Engine Valves MCQs with Detailed Explanation

Correct Answer: A. Poppet valve

• Poppet valve is the most commonly used valve in automobile engines.
• It is also known as mushroom valve because of its shape.
• It controls the flow of fresh charge into the cylinder and exhaust gases out of the cylinder.
• It is simple, economical and has good working life.

Correct Answer: B. 45 degree

• The exhaust valve works under high temperature and high pressure conditions.
• A 45° valve face angle gives proper seating and sealing for the exhaust valve.
• A larger valve seat angle can improve flow, but it may increase sliding movement and wear.
• Inlet valve seat angle is generally 30°.

Correct Answer: D. Valve springs

• The camshaft helps to open the valve at the correct time.
• When the cam lobe pushes the follower, motion is transmitted through push rod and rocker arm.
• After the cam lobe moves away, the valve spring forces the valve back to its seat.
• So, the valve spring is responsible for closing the valve.

Correct Answer: D. All of these

• The camshaft is an important part of the valve operating mechanism.
• It decides when the inlet and exhaust valves should open and close.
• The shape and position of the cam lobe control valve movement.
• Therefore, camshaft controls valve opening, valve closing and valve timing.

Correct Answer: A. Lifter, push rod and rocker arm

• The camshaft converts rotary motion into reciprocating motion through the cam lobe.
• This motion first acts on the cam follower or lifter.
• The push rod carries the motion upward to the rocker arm.
• The rocker arm finally pushes the valve against spring force and opens the valve.