Mercury F4AZ-6571-A Seal - Valve Stem

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To replace broken valve springs or defective valve stem seals without removing the cylinder heads, specific tools and compressed air are needed. Remove valve cover(s) and spark plug(s) from affected cylinder. Ensure piston is at Top Dead Center on compression stroke. Thread adapter into spark plug hole and connect air hose from compressed air source. If no air pressure, insert nylon rope into combustion chamber to prevent valve drop. Remove rocker arm, fulcrum, and pushrod for affected valve. Apply compressed air to hold valves in place. Alternatively, with rope, stuff rags into cylinder head holes, use valve spring compressor to compress spring, remove keepers, and disassemble valve components. Inspect valve stem for damage, lubricate it, and install new valve guide seal. Reassemble valve components, release air pressure or rotate crankshaft, and reinstall rocker arm(s), pushrod(s), spark plug(s), and valve cover(s). Start and run engine, check for oil leaks and unusual sounds from valve cover area.

The valve spring compressor, utilizing the camshaft as a pivot point, applies pressure to release tension on the cam follower, while the spring spacer prevents over-compression.