🔍 Key Concepts

• Four-stroke diesel cycle (intake, compression, power, exhaust) and what the valves are doing in each stroke • What "valve clearance" (lash) is and why it is set when the cam follower is on the base circle of the cam • Difference between piston at TDC on the compression stroke vs TDC on the exhaust stroke (valve positions)

💭 Think About

• In which stroke are BOTH intake and exhaust valves fully closed while the piston is at top dead center (TDC)? • When the cam lobe is NOT lifting the valve (on the base circle), how does that affect the accuracy of your valve clearance measurement? • Think about when the cylinder is ready for fuel injection and compression—what is happening with the valves at that moment?

✅ Before You Answer

• Verify at which crank position the intake and exhaust valves are completely closed for that cylinder • Confirm that clearance is set when there is no load from the cam lobe (follower on the base circle) • Check engine timing diagrams to see valve events around TDC on both compression and exhaust strokes and compare them