One can replace the broken valve springs and faulty valve stem seals without having to remove the cylinder heads but it is advisable that one read the instructions keenly and also ensure he or she has all the tools that may be required in the job. In the absence of compressed air, it is possible to wrap a nylon rope around the valves in order to prevent them from falling into the cylinder. Starting with the rocker arm cover on the cylinder head concerned, and if all the valve stem seals are being changed then both covers should be removed. Subsequently, extract the spark plug of the cylinder containing the impaired component, while in case of replacing all seals, take out all spark plugs. The thing one can do is to turn the crankshaft until the piston in the concerned cylinder is at the Top Dead Center on the Compression stroke and then proceed through fire order number one, two and so on. Insert an adapter with a hole in it into the spark plug hole and attach an air hose which is connected with a compressed air. Take out the bolt, pivot and rocker arm of the valve with the faulty part and then pulling out the pushrod. Use compressed air on the cylinder to secure the shutdown of the valves; if the faces or seats of the valves are worn, there is always a leakage. If compressed air is unavailable, place the piston just prior to TDC on the compression stroke, insert a length of nylon rope through the spark plug hole and then turn the crankshaft until one just feels a resistance. The use of shop rags can be used to eliminate the chances of having parts falling into the engine from the top of the valve stem and the usage of the valve spring compressor to compress the spring and removing the keepers. If air pressure cannot retain the valve closed then the valve face or seat will be damaged and the removal of the cylinder head is required for repair. Coil a rubber band or a tape at the top of the valve stem to allow it not to fall inside the combustion chamber and then deflate the air pressure. Check the valve stem for wear, it has to slide in the guide without sticking. Atmospheric pressure is reapplied to hold the valve in the close position, lubricate the stem of the valve with the clean oil from the engine, and put on a valve guide seal which is new. Place the keepers at the upper groove of the spring retainer followed by the valve spring retainer and tightening it, use grease at this point to hold the keepers when fitting the spring above the valve. Shut off the airflow and take out the adapter from the spark plug hole and then replace the rocker arm(s) and the pushrod(s) and finally the spark plug(s) and the wires if any. Last, place the rocker arm cover(s), turn the engine on and look for oil dripping and any strange sounds originating from the rocker arm cover place.