The spring compressor apparatus and method for compressing cylinder valve spring for the removal and installation of their locks or keepers and for replacement of valve stem seals or broken springs on an internal combustion engine, while the cylinder head is mounted on the engine or supported on a workbench. A compressor tool adjustably mounted on a support assembly temporarily secured over the cylinder head has a pivoting hand lever and spring biased push rod which, when manually depressed, moves a compressing member at the bottom of the push rod downward to engage and depress the valve spring and its retainer to gain access and removal of the lock or keeper through openings in the compressor tool.