Internal lash lifters can be replaced while the crankshaft is still in the engine, while the more complicated and time consuming substitute jobs that involve the replacement of free or broken valve springs or a defective valve stem seal seldom call for more than the removal of the cylinder head which normally demands two special tools and a source of compressed air. Under circumstances where compressed air is not possible, a piece of nylon string may be utilised to keep the valves from falling into the cylinder. Start with the dismantling of the spark plug from the cylinder having a defective part, and if all the valve stem seals are being replaced at one go, then apart from the spark plug, both the camshaft housings should also be removed. Next, it is necessary to take out the ignition coil assembly and the camshaft or camshafts and lifters as well as the housing or housings. Rotate the crankshaft until the piston of the cylinder that needs to be tested is on the TDC of the compression stroke and if replacing all the valve stem seals begin with cylinder No, 1 in the firing order. Insert an adapter in the spark plug hole and attach the other end of an air hose to a source of compressed air. Using compressed air blast the cylinder while seeing to it that the piston is not moving in the wrong direction. This should keep the valves seated to the air pressure; if not the valves may need to be ground. If compressed air cannot be used then place the piston slightly before TDC, thread a nylon rope into the combustion chamber, turn the crankshaft until one feels slight resistance. Push shop rag into other cylinder head holes, use valve spring compressor to compress the spring and take off the keepers. When the retainer and the valve spring have been taken off, look for signs of wear of the valve stem. Apply pressure to the air to maintain the valve shut; undo the tape or rubber band if used. Engine oil should then be applied on the valve stem, a new guide seal fitted and placements of the spring the of the valve done properly. Place the valve spring retainer again, and by compressing the valve spring, place the keepers rightly in position. However, turn off the air hose, retract the adapter, replace the camshaft(s), lifters and housing(s), as well as spark plug(s) and coil assembly then starting the engine and examine there and then for oil leaks or unusual noise.