Valve springs could be damaged and valve stem seal could be faulty and in most cases to replace these only one needs to take off the
Cylinder Head, and one needs two special tools and a compressed air. High plugs, plenum, intake, valve covers,
Timing Chains, cams, and rocker assemblies should be installed first. Insert an adapter to the spark plug hole and attach an air hose from an air pressure. Spray compressed air into the cylinder to secure the valves after which, a light knocking on the top of each valve spring retainer frees the valve keeper from the spring retainer to enable the compression of the spring with the help of a valve spring compressor. Pull out the keepers using needle-nose pliers or by using a magnet and thereafter, pull out the valve spring as well as the retainer. If air pressure does not suffice to keep the valve in place, it might be necessary to take off the cylinder head for purposes of repair. Take off the old valve stem seals, remember that intake stem seal is generally thinner than that of exhaust and place a rubber band or tape around the end of the valve stem so that it cannot fall into the combustion chamber when you release the air pressure. Visually check for an indications of wear on the valve stem and check to be sure if it freezes in the guide; if it does then heads will require removal for repairs. Apply pressure on the valve to lock it in then put the new valve stem seals over the ends of the valve guides making sure that an exhaust valve seal is not fitted onto an intake valve. Place the spring and retainer back on to the valve, tighten up the spring until the keepers can be reinserted, and in some cases to secure them, use a drop of grease. Release the pressure from the spring tool to allow the keepers to set properly, disconnect the air hose and lift the adapter from the spark plug hole. Perform the same for the rest of the cylinders; replace the
Rocker Arm assemblies,
Camshafts, timing chains, and the valve covers. Cranks the engine and examine for any sign of oil leakage and for strange noises, it is recommended that the engine be allowed to run for no less than five minutes before testing acceleration.