This handy tool compresses valve springs for quicker, easier camshaft, valve seal, valve spring, or retainer service--because you don't have to remove the head from the engine first! It's an OEM-approved tool that you use with a 3/8" ratchet or breaker bar. Works on: 1991¿2004 Ford vehicles with 4.6L, two-valve, V8 engines; 4.6 4V, 5.4 V8 and 6.8 V10.