How to Adjust Valves on a Four-Cylinder Engine?
3 Answers
Four-cylinder engine valve adjustment method: Rotate cylinder 1 to the compression top dead center (there is a scale on the crankshaft pulley or a mark on the crankshaft flywheel) to align with the 0 scale line or the pointer on the timing gear housing; adjust the intake and exhaust valves of cylinder 1, the intake valve of cylinder 2, and the exhaust valve of cylinder 3; then rotate 360 degrees to adjust the exhaust valve of cylinder 2, the intake valve of cylinder 3, and the intake and exhaust valves of cylinder 4. When the engine is running, the valves operate under high temperatures, and components such as the valves elongate due to thermal expansion. Therefore, a certain valve clearance must be reserved when the valves are cold to ensure that the valves and valve seats remain tightly fitted when the valves expand due to heat.
Before adjusting the valves, you need to prepare common tools such as a feeler gauge, wrench, and screwdriver. During operation, it's essential to locate the engine's top dead center, typically by rotating the crankshaft until the first cylinder's piston reaches the highest point. The specific adjustment method depends on the type of engine you have. Most older engines require manually adjusting each valve clearance one by one. Insert the feeler gauge between the rocker arm and the valve stem, selecting the thickness exactly as specified in the manual. Loosen the lock nut and then adjust the adjusting screw, checking the clearance with the feeler gauge as you go. Once adjusted correctly, tighten the lock nut. The sequence varies for each vehicle, so it's crucial not to mix up the cylinder order. This task requires exceptional patience, and after completion, remember to recheck all valve clearances to ensure they meet the standards. If you're not confident in your DIY skills, it's best to seek assistance from someone experienced to oversee the operation.
When I adjusted the valves myself, I always waited until the engine was completely cool before starting. Adjusting valves on a hot engine is definitely inaccurate because metal expands with heat and contracts with cold, changing the clearance. Before removing the valve cover, clean the surrounding area thoroughly to prevent dirt from falling into the engine. Finding top dead center is crucial—you can observe the timing marks or listen to the intake and exhaust valve states to determine it. When measuring with a feeler gauge, don't force it in or leave too much gap; the most accurate measurement is when the gauge slides with slight resistance. After adjusting a set of valves, remember to turn the crankshaft two full rotations to reset before adjusting the next set. Finally, when starting the engine, pay attention to the valve sounds: a clear ticking noise may indicate excessive clearance, while complete silence could mean the clearance is too tight.
