* Bent Pushrods/Valves: The most serious consequence. With insufficient clearance, the valve may not be able to fully close, and when the piston rises on the compression or power stroke, it can collide with the valve, bending the pushrod, valve stem, or even breaking the valve. This can cause catastrophic engine damage.
* Burnt Valves: If the valve doesn't close completely, it won't seal properly. This leads to excessive heat transfer to the valve head, potentially causing it to warp or burn.
* Reduced Engine Power: The incomplete opening of the valve restricts the flow of air and fuel into the cylinder (intake valve) or exhaust gases out of the cylinder (exhaust valve). This directly reduces the engine's power output.
* Poor Fuel Efficiency: Because of the restricted flow, the engine may run inefficiently, consuming more fuel than it should for the work being done.
* Overheating: The incomplete valve closure and reduced efficiency can lead to increased engine temperatures.
* Pre-ignition/Detonation: In extreme cases, insufficient clearance might cause the valve to remain slightly open during combustion. This can lead to pre-ignition, where the fuel mixture ignites before the spark plug fires, causing detonation (uncontrolled explosions) in the cylinder and potential damage to the engine.
* Unusual Engine Noise: While a little valve train noise is normal in some engines, excessively tight clearances will usually produce a ticking or clicking sound. This is often the first sign of a problem.
In short, too little valve clearance is far more harmful than too much. Too much clearance will lead to noise and potentially reduced performance, but too little clearance can cause serious and expensive damage. Regular checks and adjustments of valve clearances are crucial for maintaining engine health.
