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Valve Clearance Adjustment

Does the engine need valve adjustment? It depends on the age, condition and make of the vehicle you drive. Due to the widespread use of roller follower valve train designs that reduce friction and hydraulic tappets (valve lifters) that help maintain optimal valve clearance, older vehicles require more frequent valve adjustments.
If necessary, valve clearance specifications and valve adjustment procedures vary widely from manufacturer to manufacturer. For example, some recent modern engine maintenance programs require a valve clearance inspection at 60,000 miles. Some Hondas require inspection at 110,000 miles. Some manufacturers advise you to inspect your valve only if it is too noisy. Others have not mentioned valve clearance at all in their maintenance schedule. Your vehicle’s maintenance schedule should be detailed in your owner’s manual, so if you are unsure, check it first.

Types of valves and how they work:

The valve resembles a spring tension inverted golf tee that is opened by a rotating camshaft lobe, either directly on the overhead camshaft motor or by a push rod acting on the rocker arm of the valve. Over head valve motor (pushrod). Prolonged use can increase the clearance between the lobe or rocker arm and the valve stem on which they act. It often causes rattling and more engine vibrations that the driver may not notice for a while as it ramps up but needs to be adjusted to fix. With exhaust valves, as the valve or valve seat wears, the clearance narrows over time, which can reduce the so-called rush clearance between the valve and the valve train component.
The intake valve opens and closes to allow the air-fuel mixture (or air only in some modern engines) to enter the cylinder, and the exhaust valve lets the exhaust gases escape. Too much or too little valve clearance can cause the engine to not “breathe” normally and run at maximum efficiency, resulting in poor performance and disturbed idle conditions. If the clearance is too large, the valve will rattle and may damage the valve, camshaft lobe, or rocker arm in the long run. If the valve clearance is too small, the valve will not close completely, generating excessive heat and losing engine power.

How to check the valve (and when to fix it)?

If the engine makes a loud rattling noise, it may be time to adjust the valve clearance, but the knocking noise can also be caused by loose rocker arms and other components. The mechanic will not know for sure without inspecting the valve. In some engines, the valve does not make noise if the clearance is too large, but valve problems can appear in other ways. Loss of energy can indicate, for example, that the valve spring is weak or broken.
To check the valve clearance, remove the valve cap (or two valve caps for V-engines) and use a thin feeler gauge as shown in the photo above, both the intake and exhaust valves and their lobes. Or you need to measure the space between the rocker arms.
(The camshaft must be in the correct position and each valve must be fully closed for each measurement.) If necessary, adjustments require the installation or replacement of shims with specialized tools, oil Not an input / maintenance item fast delivery as the replacement. Especially in engines that have 3 or 4 valves per cylinder. Plan to pay for at least a few hours of effort and inspection in the shop.

Eliminating valve rattle is one of the benefits of properly adjusting the valve, but the motor can also be smoother and more responsive. Additionally, proper adjustment can extend the life of the valve train.

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