What is the purpose of adjusting valve clearance in a car engine?

[StellaAnn]

The purpose of adjusting valve clearance in a car engine is to compensate for the thermal expansion of the valves. When the engine is running, the valves expand due to the increase in temperature. If there is no gap or the gap is too small between the valves and their transmission components in the cold state, the thermal expansion of the valves and their transmission components will inevitably cause the valves to not close tightly in the hot state. Valve clearance is divided into cold clearance and hot clearance. Hot clearance is slightly smaller than cold clearance, and the clearance measured in the cold state of the engine is the cold clearance. Generally, the cold clearance of the intake valve is between 0.08 to 0.10 millimeters, and the cold clearance of the exhaust valve is around 0.10 to 0.12 millimeters. Adjustment should be strictly carried out according to the clearance specified in the manual. The inspection and adjustment of valve clearance must be performed when both the intake and exhaust valves are completely closed. When the piston is at the top dead center of the compression stroke, the intake and exhaust valves are exactly completely closed, so the valve clearance must be adjusted when it is at the top dead center. The adjustment of valve clearance should be performed when the engine is in the cold state. It is strictly forbidden to adjust the clearance when the engine is running. For a twin-cylinder engine, inspection and adjustment should be carried out cylinder by cylinder.

[Jason]

When it comes to adjusting valve clearance, with over a decade of experience in the repair shop, I fully understand its importance. It's mainly to address engine thermal expansion: metal components expand when heated, so leaving some valve clearance prevents burning and leakage. If the gap is too small, the valve won't seal properly, leading to compression loss, reduced power, increased fuel consumption, and even engine overheating and failure. What if it's too large? Delayed valve opening/closing, loud noise, accelerated wear, and shortened lifespan. Adjustment is typically done when the engine is cold, using a feeler gauge to measure the standard value—refer to the vehicle manual for specifications. I recommend checking every 20,000 kilometers, more frequently for older cars. Don't underestimate this task; proper adjustment can improve fuel efficiency by 10%, make operation quieter and smoother, and reduce harmful emissions—eco-friendly and hassle-free. Neglecting it in daily maintenance can double repair costs, so car owners should develop a habit of regular servicing, just choose a reputable repair shop.

[MacHarley]

Over the years of modifying cars, I've particularly valued the impact of valve clearance adjustment on performance. When the clearance is properly set, valve action becomes precise, combustion efficiency doubles, throttle response sharpens, acceleration becomes fiercer, and horsepower delivery smoother. If the gap is too large, power feels sluggish and noise becomes annoying; too small? The valves risk seizing under high temperatures, with high engine stall risk. Adjustments must be done on a cold engine—I personally use feeler gauges to match specifications. The process isn't difficult but requires patience; take breaks to avoid rushing. I often see modifiers neglect this, only to waste money on burnt engines. Remember to combine it with engine health checks for worn components like lifters. Maintaining ideal clearance can extend engine life by 20%, enhance driving pleasure, and save fuel. Regular fine-tuning lets you race worry-free on tracks.

[StLiam]

As a commuting driver, I've learned the benefits of adjusting valve clearance to prevent major issues. It leaves a gap for metal expansion and contraction with heat, ensuring proper valve opening and closing to avoid leaks or seizing, which can lead to engine power loss, increased fuel consumption, or abnormal noises. Neglecting this adjustment can turn minor faults into costly overhauls. I usually have it checked and adjusted at a repair shop every 40,000 km for convenience. Once, I ignored it and ended up with an overheated engine that stalled, costing me thousands in emergency repairs. Now, with regular maintenance including this adjustment, my engine runs much smoother with quicker starts and less noise, making the car more durable. Don't skimp on basic maintenance like oil changes—doing it early brings peace of mind.