🔍 Key Concepts

• Valve timing and tappet (valve lash) clearance in a four-stroke diesel • How increasing clearance changes when the cam lobe actually contacts and releases the valve train • Relationship between cam profile, follower motion, and the valve’s open/close points in crankshaft degrees

💭 Think About

• Visualize the cam lobe and follower: if you increase the clearance, does the valve start to move sooner or later for the same cam position? • Once the cam lobe has passed its peak and is coming back down, with more clearance, will the valve stop moving (close) sooner or later? • Think about whether extra ‘slack’ in the system makes the valve spend more or less time off its seat.

✅ Before You Answer

• Confirm what tappet (valve lash) clearance physically is (the small gap between parts when the valve is fully closed). • Mentally sketch the cam lobe vs. valve lift diagram and see how adding clearance shifts the points where lift becomes zero and non-zero. • Verify whether more clearance increases or decreases the duration of valve opening in crankshaft degrees.