CAUTION: Broken valve springs and damaged valve stem seals can be replaced without removing the cylinder head. This operation usually requires special tools and a source of compressed air, so read this section carefully and purchase or rent the necessary tools before beginning the job. If you do not have a source of compressed air, you can use a piece of nylon rope to prevent the valves from falling into the cylinder while you perform this operation.
Remove the cover from the cylinder head.
Remove the camshaft (see above).
Remove all spark plugs.
Rotate the crankshaft so that the piston of the desired cylinder is at TDC of the compression stroke. When replacing all valve stem seals, start with the first cylinder and work on each cylinder in turn. Go from cylinder to cylinder in the firing order (1-3-4-2).
Screw the adapter into the spark plug hole and attach a hose from a compressed air source to it. Most auto parts stores sell this adapter. Many cylinder compression testers use a screw-in adapter that can be installed in this case.
Direct compressed air into the cylinder.
CAUTION: The piston may be forced downwards by compressed air, causing the crankshaft to rotate unexpectedly. If the wrench used to set the first piston to TDC is still attached to the bolt at the front end of the crankshaft, it may cause injury if the crankshaft rotates unexpectedly.
Valves should be held in place with compressed air. If the valve or seat surfaces are in poor condition, leaks may prevent compressed air from holding the valves - see the alternative method below.
CAUTION: If the compressed air pressure does not hold the valve closed during this operation, the valve face or seat is probably damaged. If this is the case, the cylinder head will have to be removed for repair.
If you do not have a source of compressed air, you can use an alternative method.
To do this, set the piston to the position before TDC on the compression stroke, then pass a long piece of nylon rope through the spark plug hole until it fills the combustion chamber. Be sure to leave the end of the rope hanging out of the engine so that it can be easily removed. Using a large wrench, turn the crankshaft in the normal direction of rotation until a slight resistance is felt.
Place a clean rag in the cylinder head openings above and below the valves to prevent parts and tools from falling into the engine, then use a special spring compressor. Remove the crackers (5) with small, pointed pliers or a magnet.
Remove the plates (4 and 1) of the spring (3), the valve spring, then remove the seal (2) of the guide.
Place a rubber band or tape around the top of the valve stem to prevent the valve from falling into the combustion chamber, then release the air pressure.
CAUTION: If a nylon rope was used instead of air pressure, turn the crankshaft slightly in the direction opposite to normal rotation.
Check the valve stem for damage Rotate the valve in the guide bushing and check for movement of the eccentric at the end, which would indicate that the valve is bent
Move the valve up and down in the guide bushing and make sure it does not stick. If the valve stem sticks, either the valve is bent or the guide bushing is damaged. In either case, the head must be removed for repair.
Apply air pressure to the cylinder again to hold the valve closed, then remove the rubber band or film from the valve stem. If a nylon rope was used, turn the crankshaft in the normal direction of rotation until a slight resistance is felt.
Place the spring back over the valve.
Lubricate the valve stem with engine oil and install a new seal.
Install the spring mount (cotters). Compress the spring with the spring puller and carefully insert the cotters into the groove. Apply a small amount of grease to the inside of each mount to hold it in place.
Relieve pressure from the compressor and ensure that the crackers are properly seated.
Use a rubber hammer to tap the valve.
Disconnect the compressed air hose and remove the adapter from the spark plug hole. If a nylon rope was used instead of compressed air, pull it out of the cylinder.
Refer to the previous section and install the camshaft.
Install the spark plugs and connect the high tension wires.
Install the cylinder head cover.
Start the engine and let it run, then check for leaks or unusual sounds coming from the valve cover.
