🔍 Key Concepts

• Valve train components: valve stem, rocker arm or cam follower, pushrod, camshaft • Thermal expansion of engine parts and why moving parts need clearance • Purpose of setting valve clearance/lash during engine maintenance

💭 Think About

• Which two parts must have a small gap so the valve can fully close as the engine heats up and parts expand? • Which options describe something that is actually a gap/clearance versus a force or a shape? • When mechanics "adjust valve lash" on a diesel, what are they adjusting with a feeler gauge under the rocker arm or adjusting screw?

✅ Before You Answer

• Verify which choice clearly describes a physical gap between two valve train parts that move against each other. • Eliminate any option that describes spring force or cam shape, since those are not clearances. • Think about what you physically measure with a feeler gauge when setting valve lash on an engine.