What Causes Loose Valve Guide Wear?

[LaRhett]

Valve guide wear and looseness can be caused by poor lubrication of the valve guide, insufficient interference fit between the valve and valve guide, or a bent valve stem, which can also cause the valve to stick during movement within the guide. Poor Lubrication of Valve Guide: After the valve guide wears out, the clearance between the valve guide and valve stem increases, allowing gasoline to easily leak into the cylinder through the gap from the intake valve. This worsens oil consumption and leads to carbon buildup, which can clog the starting spray hole and make engine starting difficult. It is recommended that owners improve the lubrication of the guide. Insufficient Interference Fit Between Valve and Valve Guide: It is recommended that owners adjust the interference fit. A Bent Valve Stem Can Also Cause the Valve to Stick in the Guide: There is usually a small gap between the valve stem and valve guide to allow the valve stem to move freely within the guide. The valve guide operates at high temperatures with poor lubrication. Typically, valve stems are made of high-graphite cast iron or iron-based powder metallurgy to enhance self-lubricating properties.