What are the methods for adjusting valve clearance?
3 Answers
Adjusting valve clearance involves the following steps: 1. Based on the firing order of the cylinders, determine when a particular piston is at the top dead center of the compression stroke, then adjust the intake and exhaust valve clearances for that cylinder; 2. After completing the adjustment, rotate the crankshaft and proceed to adjust the valve clearances for the remaining cylinders in the same manner. Valve clearance is categorized into cold engine values and hot engine values, and measurements should be taken under the conditions specified for the vehicle. When the engine is running, the valves expand due to increased temperature. If there is no clearance or insufficient clearance between the valves and their transmission components when cold, thermal expansion during operation will cause the valves to not close properly, leading to leakage during the compression and power strokes. This results in reduced power output and, in severe cases, difficulty starting. To prevent this, a certain clearance is typically maintained between the valves and their transmission components when the engine is assembled cold, to compensate for thermal expansion. This clearance is known as valve clearance.
Let me share practical insights on valve clearance adjustment methods. The most common approach is manual adjustment - you must wait until the engine completely cools down first. Open the valve cover to locate the gap between the rocker arm and pushrod. Use a feeler gauge (that thin steel ruler) to measure whether it falls within manufacturer specifications. Typically you'll need to rotate the engine until the camshaft reaches top dead center in the compression stroke. Too tight and your engine will sound terrifying at startup; too loose and power delivery becomes uneven. Use wrenches to carefully turn those adjustment nuts - go slowly without excessive force. Many veteran mechanics overlook this critical step: after each adjustment, start the engine and test-drive several laps before rechecking. This prevents oil leaks or noise issues while extending engine lifespan.
Here are some DIY tips for adjusting valve clearance yourself. First, gather the necessary tools: a reliable feeler gauge and a suitable wrench. Make sure the car is parked on a level surface and has cooled down overnight. Then, pop the hood and remove the valve cover to expose the valve components. Manually rotate the crankshaft until it stops in the camshaft's low-pressure zone. Insert the feeler gauge between the rocker arm and valve stem to check if the clearance is appropriate. Too tight, and the engine will keep making noise; too loose, and you'll notice a significant drop in horsepower. Use the wrench to fine-tune the adjusting nut, turning it little by little—no rush. Once done, immediately reinstall the cover, start the engine, and listen for smooth operation—if it sounds good, you're all set. I've saved on repair costs by doing this at home, but beginners should start with simpler car models and avoid tackling more complex vehicles right away.
