Practice question

What is the purpose of lapping (grinding) a valve against its seat using lapping compound during a top-end overhaul?

To create a smooth, matching contact surface between the valve face and seat so the valve seals properly during compression and combustion
To increase the size of the valve permanently
To clean carbon deposits from the spark plug
To adjust the ignition timing

Answer: A — To create a smooth, matching contact surface between the valve face and seat so the valve seals properly during compression and combustion

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