The engine top end includes components such as the cylinder head, valves, camshafts, and related parts that control the intake and exhaust processes of the engine.

The valve clearance should be inspected every 42,000 km (26,000 miles) to ensure the valves operate correctly and to prevent engine damage.

Signs of improper valve clearance include poor engine performance, unusual engine noises, difficulty starting the engine, and reduced fuel efficiency.

To adjust the valve clearance, remove the cylinder head cover, measure the clearance with a feeler gauge, and adjust the clearance by changing the shims or adjusting screws according to the specifications in the manual.

The camshaft controls the opening and closing of the engine's valves by pushing on the valve lifters, which in turn operate the valves. Proper timing of the camshaft ensures efficient engine operation.

Inspect the camshaft and its bearings for signs of wear, scoring, or damage. Use a micrometer to measure the camshaft lobes and journals, comparing the measurements to the service limits specified in the manual.

To replace a damaged valve, remove the cylinder head, compress the valve spring, remove the valve keepers, and take out the valve. Install the new valve by reversing these steps and ensuring proper seating and clearance.

Inspect the cylinder head for warping using a straight edge and a feeler gauge. Place the straight edge across various points of the cylinder head surface and measure any gaps with the feeler gauge. Compare the measurements to the service limits specified in the manual.

Valve springs maintain pressure on the valves, ensuring they close completely after opening. Proper valve spring tension is crucial for valve timing and engine performance.

To test the valve seats for proper sealing, perform a leak test by applying a light oil to the valve seats and observing if any oil seeps through when the valves are closed. Alternatively, use a vacuum tester to check for proper sealing.