Note: Broken valve springs and defective retainer seals can be replaced without removing the cylinder head. This operation usually requires two special tools and a source of compressed air, read this section carefully before beginning. If compressed air is not available, a nylon rope will be needed to prevent the valves from falling into the cylinders during operation
1. Remove the valve cover from the cylinder head (see section 3).
2. Remove the spark plug from the cylinder with the faulty valve. If you are replacing all the valve stem seals, remove all the spark plugs.
3. Turn the crankshaft so that the piston in the selected cylinder is at TDC in the compression stroke (see instructions in section 5).
If you are replacing all the valve stem seals, start with cylinder #1, then work on each cylinder one at a time. Go from cylinder to cylinder in the firing sequence (1-3-4-2).
4. Screw the adapter into the spark plug hole and connect an air hose from a compressed air source to it.
Note: Many cylinder pressure sensors use a screw-in connector, this can also be used as a quick connect air hose.
5. Remove the valve lever retaining bolt, valve lever, hinge pin and push rod from the defective valve. If all valve stem seals are being replaced, all levers and push rods must also be removed (see section 4).
6. Apply compressed air to the cylinder. The valves should be held in place by the air pressure. If the condition of the outer surfaces or valve seats is unsatisfactory, the valves will not be held by the pressure due to leaks - for this case, see the recommendations below.
7. If you don't have access to compressed air, another method is to set the piston to just before TDC on the compression stroke, then thread a long piece of nylon string through the spark plug hole until it fills the combustion chamber. Make sure the other end of the string hangs out so you can pull it out easily. Use a large ratchet and socket to turn the crankshaft in the direction it rotates until you feel a slight resistance
8. Plug the oil return holes in the cylinder heads with rags to prevent parts from falling into the engine, then use a valve spring puller to compress the spring assembly. Remove the crackers with small needle-nose pliers, a magnet, or tweezers (see illustration).
Note: It is possible to use two different types of tools to compress the valve spring without removing the head. One tool grips the bottom rings and compresses the others when the handle is turned, the other (shown in the picture) uses the valve lever retainer bolt as a lever.
9. Remove the spring retainer and valve spring assembly and set aside. Using pliers, remove the valve stem seal (see illustration) and discard.
Note: If the air pressure is not sufficient to keep the valve closed during operation, it is likely that the outer surface or seat of the valve is damaged. In this case, it is necessary to remove the cylinder head and perform additional repairs.
10. Wrap electrical tape around the top of the valve stem to prevent it from falling into the combustion chamber, then release the air pressure.
Note: If you used a rope instead of air pressure, turn the crankshaft slightly in the opposite direction to its normal rotation.
11. Inspect the valve stem for possible damage. Rotate the valve in the guides and watch for the end of the eccentric movement, which will indicate that the valve is bent
12. Move the valve up and down the guides and make sure it does not stick. If the valve stem sticks, it means the valve is bent or the guides are damaged. In this case, you need to remove the head for repair
13. While building up air pressure in the cylinder, return the valve to the closed position, then remove the rubber gasket or tape from the valve stem. If you used a rope, turn the crankshaft in the direction of its normal rotation until you feel slight resistance
14. Lubricate the valve stem with engine oil and install a new seal onto the valve stem. Use a 5/8" socket and a hammer to firmly seat the seals onto the valve guides (see illustration). Remember that intake seals have a wide band at the base and a ring on top, while exhaust seals have two rings.
15. Replace the valve spring assembly and carefully install the keepers into the grooves of the valve stem. Apply a small amount of grease to the inside of each keeper to help them stay in place
17. Release the pressure of the tool on the spring, make sure that the holders are in place.
18. Disconnect the air hose and remove the adapter from the spark plug hole. If a rope was used instead of air pressure, remove it from the cylinder.
19. According to the recommendations given in section 4, install the valve lever and push rod.
20. If you are replacing all the seals, repeat the procedure for each valve assembly. Remember that before removing the valve cotters, the piston of each cylinder must be set to TDC.
21. Install the spark plugs and connect the wires.
22. Install the valve cover (section 3).
23. Start and warm up the engine, then check for oil leaks and unusual sounds that may come from the valve cover area.