Exhaust and intake valve springs may be replaced with the cylinder heads in the car, though they may need to be removed if the seats or seals on the stems have worn; replacement of these usually requires two specialized tools and compressed air. In case compressed air is not available, a piece of nylon rope can be employed such as to keep the valves from falling inside the cylinder. First, take off the valve cover of the cylinder head, which unfortunately need to be changed, and if all the valve stem seals are being replaced, the two covers. The next step is to remove the spark plug which will be located within the cylinder containing the faulty part ; if changing all seals this will require the removal of all spark plugs. Rotary the crankshaft in such a manner that the piston in the required cylinder is on the TDC of the compression stroke starting with cylinder no 1 and then following the firing sequence. Place the adapter to the spark plug hole, then attach the other end of the air hose to the compressed air. It is recommended that rocker assembly of the failed side be pulled off and, if replacing all the seals, remove both of them. To do this, the compressor should be connected to the cylinder, the valves should be secured in place in the cylinder. Have to use shop rags to block such holes on the cylinder head so that none of the parts drops inside the engine. Loosen the machine by rotating a valve spring adjuster and squeezing the valve spring by a valve spring compressor. After you have had your spring retainer and your valve spring removed, you also have to remove the valve stem seal. If the pressure of air does not shut the valve then the face or the seat of the valve is likely to be chafed, requiring the cylinder head to be pulled for repairs. Place the tip of the valve stem in the slot and wind a rubber band or some tape around the stem head to avoid it falling into the combustion chamber, then discharge the pressure. Check the valve stem for damage and the movement should be smooth without having to force the stem within the guide. Apply air pressure to maintain the closure of the valve and then, remove the tape or rubber or any such band. Cover the valve stem with engine oil and then put a new stem seal by using the seal installer tool. Align the spring over the valve; fit the valve spring retainer; compress the spring and the valve stem locks are put in while a drop of grease is used to hold the locks firmly. Release the pressure from the spring tool and make sure that the lock are properly positioned. Remove the air hose and take off the adapter from the spark plug hole and put in the rocker arm assembly, the spark plug or plugs with the wire, or wires and valve covers as appropriate. Last but not the least, turn on the ignition and look for the signs of oil dripping down on areas aside the valve cover and any strange sounds emanating from the areas.
