Both valve springs and valve stem seals can be changed without even having to uninstall the cylinder head; the procedure requires two tools, and a source of compressed air. Start with the spark plugs and the valve covers, proceed and turn the crankshaft until the first piston is at the top on the compression stroke. Take off the rocker arms for the number 1 piston, screw in an adapter into the spark plug hole and join a hose to an air compressor. Expel compressed air in the inside of the cylinder lid in order that the valves be closed that would continue holding these in position and stuff shop rags into the holes found on the head of the cylinder so as to avoid loss of parts and tools into the engine. Hammer on the top of each valve spring retainer lightly to burst the seal and remove the outer keepers using a valve-spring compressor, a magnet or small needle-nose pliers while compressing the spring. If air pressure is for some reason unable to keep the valve closed the face of the valve or seat can become badly worn and the cylinder head is usually then removed for reconditioning. Pop off the old valve stem seals, in EN intake and EXHAUST, and around the top of the valve stem wrap a rubber band put some tape so the stem will not fall into the combustion chamber before cutting the air pressure off. Check valve stem for wear and tear, if bent it will not move freely in the guide and the head has to be taken off for straightening. Again apply the air pressure to lock it in the closed position and then fit the new valve stem seals to the required depth and do not hamper their installation by pushing against the top of the guide. Place the spring and retainer over the valve, crush the valve spring assembly to fit the keepers on the valve stem groove and use a small amount of grease if required to do so. Release pressure inside the spring tool and make sure that the keepers are fitted properly; then detach the air hose and the remove the adapter from the spark plug hole. Perform the said process for the rest of the cylinders; carefully turning the engine to have each piston at Top Dead Center on the compression stroke then regulating air pressure. Last of all, replace the rocker arm assemblies along with the valve covers, start the engine and examine the amount of oil dripping and also any sort of odd noises to be produced by the engine which should be allowed to idle for not less than five minutes then race the engine.
