If you want to replace damaged or worn out valve stem seals as well as broken valve springs without removing the cylinder heads,Begin by taking off the rocker arm assembly then the valve cover (s), and finally, you can remove the lifter guide assembly. Unscrew the spark plug from the affected cylinder (or all spark plugs if replacing all valve stem seals) and make sure the piston in that cylinder is at Top Dead Center on compression stroke moving through firing order sequence where necessary. Screw a long adapter into the spark plug hole and connect it to compressed air source. Introduce compressed air into the cylinder as well as place shop rags around each of the valves to prevent debris from falling into engine. Use pliers or magnet to remove them after releasing the valve keepers and compressing spring with a valve spring compressor. Ensure valves are kept in place using air pressure because poor face or seat conditions may cause air leaks. Take off the shield, spring retainer, valve spring and finally, remove the valve stem seal. Before releasing air pressure, secure its valve stem by using a rubber band or tape so that it will not slip down into combustion chamber. In case of binding between guide and stem, head should be removed for repair since it indicates either a damaged guide or valve which is extremely bad news when things like this happen inside an engine in motion. Reapply pressure again which would hold close both exhaust and intake valves, while taping is released along with booting of oils on new stems of valves before installing new ones too into guides meant for each cylinder's own sets of valves also being pushed down according to acceptable depth by tapping such until they become fully seated with their respective shoulders against top surface of cylinder head. The tool used for this purpose can be a socket extended deep inside of engine upon applying light blows with a hammer so that it fits up tightly just within limits allowed by configurations drawn up by manufacturers for an intake valve seal. Place exhaust seals in as far as just internal fingers will allow as soon as you see them ready to go home to the bottom of their respective counterbores. Be careful enough not to mix up intake and exhaust seals. Install the inner and outer springs with closely-wound coils against the cylinder head, then put the valve spring retainer on and finally, hold keepers in groove gently applying some grease to help keep them in place temporarily at least until pressure is off from such a tool of theirs for retention purposes. Remove pressure from the spring tool and ensure that keepers have been seated correctly. Disconnect air hose and adapter, install lifters assembly, rocker arm assembly, valve cover(s), spark plug(s) and wires. Start engine; check oil leaks as well as unusual sounds coming from valve cover area.
