Session 1: Reconditioning of Valve MechanismTextual Question-Answers
Module 2: Serviceability, Replacement, or Repair of Engine Components
Know Your Progress
Fill in the blanks
1. The valve mechanism controls the submission of inlet gases andemission of exhaust gases in relation to the rotation of the …………….
Ans: crankshaft
2. Valve ……………. is necessary to diagnose leakages of combustion gases and improve engine performance.
Ans: testing
3. During the valve lapping operation, abrasive/emery paste is appliedon the valve face, and the lapping stick is turned in both clockwise andanticlockwise directions to ensure proper sealing between the valveand …………….
Ans: valve seat
4. The Overhead Cam (OHC) mechanism consumes less enginepower for valve operation and is located at the …………….
Ans: cylinder head
Multiple Choice Questions
1: Which of the following components controls the timing andquantity of gas or vapor flow into an engine?
(a) Piston rings
(b) Rocker arm
(c) Valve
(d) Camshaft
Ans: (c)
2: What is the primary reason for conducting a compression test ofan engine’s valve mechanism?
(a) To measure fuel efficiency
(b) To check for coolant leaks
(c) To assess valve leakage
(d) To evaluate oil pressure
Ans: (c)
3: In an Overhead Cam (OHC) mechanism, where is the camshaftfixed?
(a) In the crankcase
(b) In the cylinder head
(c) On the rocker arm
(d) In the valve guide
Ans: (b)
4: What is the purpose of the valve lapping operation duringreconditioning?
(a) To measure valve leakage
(b) To replace damaged valves
(c) To adjust valve tappet clearance
(d) To ensure proper sealing between the valve and valve seat
Ans: (d)
Answer the following questions
Q1. What is a poppet valve?
Ans: A poppet valve is a type of valve used in IC engines to control theentry of fresh charge and exit of exhaust gases by opening and closing theports.
Q2. How many kinds of valve used in IC Engine?
Ans: Two kinds of valves are used in an IC engine, namely inlet valve and the exhaust valve.
Q3. What are the purposes of a valve?
Ans: The purpose of a valve is to admit air or air-fuel mixture into thecylinder and to discharge exhaust gases from the cylinder at the correct time.
Q4. Briefly describe a function of a valve & draw its line diagramswith details.
Ans: The function of a valve is to open and close the inlet and exhaust ports in proper sequence with engine operation to control gas flow.
Note: Students should draw a neat line diagram of an engine valve and label its parts.
Q5. What are the seat angles & why it is required?
Ans: The common valve seat angles are 30°, 45°, and 60°. These angles arerequired to ensure proper sealing, better heat transfer, and longer valve life.
Q6. Which part control opening & closing of a valve?
Ans: The camshaft controls the opening and closing of a valve.
Q7. Write the name of the tools required for valve seat grinding.
Ans: Valve grinding machine, lapping stick, emery paste, valve springcompressor, and cleaning brush.
Activity
1. Make a list of reasons for valve leakage in a vehicle.
Ans:
Sl. No. Reason
1. Worn or burnt valve
2. Damaged valve seat
3. Improper valve seating
4. Carbon deposits on valve face
2. Make a poster showing the engine valve and label its parts.
Ans:
