UNIVERSAL VALVE SPRING COMPRESSOR This valve spring compressor tool is designed to compress valve springs on overhead valve engines. It includes two valve spring adapters, which fit valve spring retainers up to 1 inch (25mm) and 1-3/16 inches (30mm). This Valve Spring Compressor is designed with a direct action compressor lever which gives better visibility of valve spring retainers located in difficult or hard to reach areas.