Disassembly tip. Lay the head on your nice flat surface, combustion chamber down. Take a deep socket that is a little smaller than the valve retainer, set it on the retainer and smack the top of the socket with a hammer. The valve will unseat and the keepers will unstick from the retainer. Then the valve compressor will have no problem compressing the springs. I watched a heavy line tech disassemble a head in about 30 seconds because he felt comfortable enough to hit the socket hard enough that the keepers just jumped out and the retainer, spring and valve flew apart.