To start with, rotate the crankshaft until the number one piston is at Top Dead Center on the compression stroke. Put an adaptor into the spark plug hole and connect an air hose from a compressed air source to it. Then you apply compressed air to the cylinder to hold the valves in place. Prevent any parts or tools from falling into the engine by stuffing shop rags into the cylinder head holes around the valves. Tap gently on top of each valve spring retainer with a socket and hammer in order to break the seal between the valve keeper and the spring retainer. Use a small pair of needle nose pliers or a magnet to remove keepers compressed spring using valve-spring compressor. Remove both spring and retainer then replace old valve stem seals. Check whether there is any damage on the valve stem or eccentric movement or binding. If necessary, remove head for repair. Press new stem seals over valve guide until they are at specified depth. Install keepers in valve stem grooves by compressing spring and placing retainers then drop them in said sequence if need be use grease literally just to stick them down tiny bit of grease will do it this time if needed at all . Follow this process for other cylinders in line with their firing order sequence as shown below: Finally, reinstall rocker arm assemblies and valve covers; start engine, check for oil leaks or any other unusual sounds that may be heard from it. Leave engine idling for at least five minutes before revving it.