Valve Spring Compressor
A tool used to compress valve springs to allow removal or installation of valve keepers and valve train disassembly.
A valve spring compressor is a mechanical tool designed to compress the valve spring in a cylinder head. Compressing the spring relieves the tension holding the valve spring retainer up against the valve keepers (locks), allowing the locks to be removed with a magnet. Once the keepers are removed, the spring tension is slowly released, allowing the valve spring, retainer, and valve to be removed.
Valve spring compressors come in several styles: C-clamp style (for cylinder heads removed from the engine), overhead valve (OHV) lever style, and overhead cam (OHC) style (which can compress the springs while the cylinder head is still mounted on the engine block). Because valve springs have very high spring rates, compressing them requires a sturdy, reliable tool to prevent the spring from slipping and shooting out under force.
When replacing valve stem seals or broken springs with the cylinder head still on the engine, the mechanic must fill the cylinder with compressed air or thread a rope into the spark plug hole to keep the valves from falling down into the cylinder bore once the keepers are released. Using the proper compressor ensures the valve stem is not bent or scratched during the procedure.