The valve springs and/or valve stem seals can be removed and installed with the cylinder head on the engine, provided that an air compressor and spark plug port fitting is available to keep the valves from falling into the combustion chambers. For details, please refer to the Valve Spring or Seal Replacement On Engine procedure found later in this section.
REMOVAL & INSTALLATION
See Figures 1 through 11
- Block the head on its side, or install a pair of head-holding brackets made especially for valve removal.
- Using a socket slightly larger than the valve stem and keys (keepers), place the socket over the valve stem and gently hit the socket with a plastic hammer to break loose any varnish buildup.
- Remove the valve keys, retainer, spring shield and valve spring using a valve spring compressor (a threaded-jawed compressor or a locking C-clamp type is the easiest kind to use, but Ford recommends a lever-type on most of these engines).
- Put the parts from each valve in a separate container numbered for the cylinder and valve being worked on; do not mix them with other parts removed.
- Remove and discard the valve stem oil seals. A new seal will be used at assembly time.
- Remove the valves from the cylinder head and place them, in order, through numbered holes punched in a stiff piece of cardboard or in a wooden valve holding rack.
The exhaust valve stems, on some engines, are equipped with small metal caps. Take care not to lose the caps. Make sure to reinstall them at assembly time. Replace any caps that are worn.
- If a complete valve job is planned, use an electric drill and rotary wire brush to clean the intake and exhaust valve ports, combustion chamber and valve seats. In some cases, the carbon will need to be chipped away. Use a blunt pointed drift for carbon chipping. Be careful around the valve seat areas.
Cleaning the combustion chambers and valve seats with the valves removed is not recommended if a valve job is not being performed because of the possible danger to proper valve seal. For heads which are not getting a complete valve job, the cleaning performed earlier under Cylinder Head cleaning and inspection will suffice.
- Use a wire valve guide cleaning brush and safe solvent to clean the valve guides.
- Clean the valves with a revolving wire brush. Heavy carbon deposits may be removed with the blunt drift.
When using a wire brush to clean carbon on the valve ports, valves etc., be sure that the deposits are actually removed, rather than burnished.
- Wash and clean all valve springs, keepers, retaining caps etc., in safe solvent.
- Clean the head with a brush and some safe solvent and wipe dry.
- Check the head for cracks. Cracks in the cylinder head usually start around an exhaust valve seat because it is the hottest part of the combustion chamber. If a crack is suspected but cannot be detected visually, have the area checked with dye penetrant or other method by the machine shop.
After all cylinder head parts are reasonably clean, check the valve stem-to-guide clearance. If a dial indicator is not on hand, a visual inspection can give you a fairly good idea if the guide, valve stem or both are worn.
- Insert the valve into the guide until slightly away from the valve seat. Wiggle the valve sideways. A small amount of wobble is normal, excessive wobble means a worn guide or valve stem.
- If a dial indicator is on hand, mount the indicator so that the stem of the valve is at 90° to the valve stem, as close to the valve guide as possible. Move the valve off the seat, and measure the valve guide-to-stem clearance by rocking the stem back and forth to actuate the dial indicator.
- Measure the valve stem using a micrometer and compare to specifications to determine whether stem or guide wear is causing excessive clearance.
- The valve guide, if worn, must be repaired before the valve seats can be resurfaced. Ford supplies valves with oversize stems to fit valve guides that are reamed to oversize for repair. The machine shop will be able to handle the guide reaming for you. In some cases, if the guide is not too badly worn, knurling may be all that is required.
- Reface, or have the valves and valve seats refaced. The valve seats should be a true 45° angle. Remove only enough material to clean up any pits or grooves. Be sure the valve seat is not too wide or narrow. Use a 60° grinding wheel to remove material from the bottom of the seat to raise and a 30° grinding wheel to remove material from the top of the seat to narrow it.
Valve and Seat refacing are best left to the professional. The high degree of skill and specialty tools necessary, not to mention the importance of this work in relation to the performance of your engine after assembly should be reasons enough in this matter.
- After the valves are refaced by machine, it may be necessary to hand lap them to the valve seat. Check with your machine shop to determine if the machining techniques used require, and the metals of the valve/seat will benefit from, hand lapping. If you determine that lapping is necessary, remember to clean the grinding compound off and check the position of face-to-seat contact after you are finished. Contact should be close to the center of the valve face. If contact is close to the top edge of the valve, narrow the seat; if too close to the bottom edge, raise the seat.
- Valves should be refaced to a true angle of 44°. Remove only enough metal to clean up the valve face or to correct run-out. If the edge of a valve head, after machining, is 1 / 32 in. (0.8mm) or less replace the valve. The tip of the valve stem should also be dressed on the valve grinding machine, however, do not remove more than 0.010 in. (0.254mm).
- After all valve and valve seats have been machined, check the remaining valve train parts (springs, retainers, keepers, etc.) for wear. Check the valve springs for straightness and tension.
- Install the valves in the cylinder head, and if equipped, the metal caps.
- Install new valve stem oil seals.
- Install the valve keys, retainer, spring shield and valve spring using a valve spring compressor (again, threaded type or the locking C-clamp type is the easiest kind to use, especially if the head is off the engine and NOT secured in a holding fixture).
- Check the valve spring installed height, shim or replace as necessary.
CHECKING VALVE SPRINGS
Spring Free Height and Squareness
See Figures 12, 13 and 14
If you have a caliper gauge, measure the free height of the spring. If a caliper gauge is unavailable, you can use a carpenter's square for both necessary measurements. Place the valve spring on a flat surface next to a carpenter's square. Measure the height of the spring, and rotate the spring against the edge of the square to measure distortion. If the spring height varies (by comparison) by more than 1 / 16 in. (1.6mm) or the distortion exceeds 1 / 16 in. (1.6mm), replace the spring.Spring Pressure
See Figure 15
Have the valve springs tested for spring pressure at the installed and compressed (installed height minus valve lift) height using a valve spring tester. Springs should be within one pound, plus or minus each other. Replace springs as necessary.Spring Installed Height
See Figure 16
After installing the valve spring, measure the distance between the spring mounting pad and the lower edge of the spring retainer. Compare the measurement to specifications. If the installed height is greater than specification, add shim washers between the spring mounting pad and the spring. Use only washers designed for valve springs, available at most parts houses.
VALVE STEM OIL SEALS
See Figures 17, 18 and 19
The old valve stem seals MUST be removed and discarded whenever the valves are removed from the cylinder head. When installing the new valve stem oil seals, be sure that a small amount of oil is able to pass the seal to lubricate the valve stems and guide walls, otherwise, excessive wear will occur. New seals will normally have an installation cap on them which must be removed after positioning, but be sure to oil the surface of the cap to help ease seal installation.
VALVE AND SEAT REFACING
See Figures 20 through 24
If the valve seat is damaged or burnt and cannot be serviced by refacing, it may be possible to have the seat machined and an insert installed. Likewise, a damaged valve face should be carefully examined to determine if refacing is possible, or if the valve should be replaced. Consult an automotive machine shop for their advice.
The high degree of precision in modern machining equipment, coupled with the extremely hard metals available for valves and seats today often make valve lapping unnecessary. But, it is best to consult with your machine shop to see if the techniques and materials used might benefit from lapping before final valve installation. If lapping is recommended use the following procedure along with their advise.
- Invert the cylinder head so that the valve faces and combustion chambers are facing upward.
- Lubricate the valve stems lightly with clean engine oil, then coat the valve seats with lapping compound. Install the valves into the cylinders as numbered, making sure no lapping compound enters the guide.
- Moisten and attach the suction cup of a valve lapping tool to the valve head.
Valve lapping can also be accomplished by fastening the suction cup to a piece of drill rod mounted to an egg beater type drill. Proceed with the lapping, using the drill as the lapping tool, BUT due to the higher speeds involved when using a hand drill, care must be taken to avoid grooving the seat. Lift the tool and change the direction of rotation often.
- Rotate the tool between your palms, changing position and lifting the tool often to prevent grooving. Lap the valve until a smooth polished seat is evident. You may have to add a bit more compound after some lapping is done.
- Remove the valve and tool, then remove ALL traces of the grinding compound with a solvent-soaked rag or rinse the head with solvent.
See Figures 25, 26 and 27
Worn valve guides can, in most cases, be reamed to accept a valve with an oversized stem. Valve guides that are not excessively worn or distorted may, in some cases, be knurled rather than reamed. However, if the valve stem is worn reaming for an oversized valve stem is usually the better answer since a new valve will be required.
Knurling is a process in which metal is displaced and raised, thereby reducing clearance. Knurling also produces excellent oil control. The possibility of knurling instead of reaming the valve guides should be discussed with a machinist.
SPRING OR SEAL REPLACEMENT ON ENGINE
See Figures 28 and 29
Under certain circumstances the replacement of one or more valve springs, seals or related components may be desired without removing the cylinder head for complete overhaul. The only problem this usually posses is that the valve will usually fall into the combustion chamber the second that the valve keys are removed. This can be prevented by pressurizing the combustion chamber (assuming the cylinder is at TDC of the compression stroke so that both valves are closed to hold the pressure) with the help of an air compressor and spark plug port fitting.
If the valve cannot be held up by air pressure (and the piston is at TDC of the compression stroke) it is likely that the valve is damaged or burnt and the cylinder head should then be removed and serviced anyway.
- Remove the rocker arm cover as described earlier in this section.
- Obtain a spark plug port fitting for your air compressor, then remove the spark plug from the cylinder being serviced and thread the fitting into the port.
- Make sure the piston for the cylinder being serviced is at TDC of the compression stroke and both valves are closed.
- For the 2.3L engine, remove the rocker arm (cam follower) as described earlier in this section.
- For the 5.0L engine, remove the rocker arm assemblies, as described earlier, then remove the pushrods for the cylinder being serviced. MAKE SURE that all parts are tagged or labelled to assure installation in the proper locations.
- Pressurize the cylinder with a minimum of 140 psi (965 kpa) of compressed air.
Keep in mind that if air pressure forces the cylinder to the bottom of its travel, any release of air pressure will allow the valve(s) to fall into the cylinder, requiring cylinder head removal for retrieval. As this is exactly what we are trying to avoid with this procedure, a little bit of insurance in the form of a rubber band, tape or string wrapped around the end of the valve stem can help prevent this possibility and still allow enough room to work.
- Using a suitable lever type spring compressor such as T88T-6565-BH for the 2.3L engine or T70P-6049-A for the 5.0L engine, depress the spring to free the valve keys (also known as locks or keepers). Carefully remove the locks and slowly release the spring tension, then remove the spring retainer.
- Remove the valve spring and, if needed, the valve stem seal. Discard the components being replaced.
- If the valve stem seal is being replaced, carefully drive the new seal into position.
- Position the valve spring and retainer, then compress the spring using the lever tool and install the keys.
- Carefully release the air pressure, then remove the spark plug adapter and reinstall the spark plug.
- Install the pushrod and/or the rocker arm assembly (cam follower on the 2.3L engine), as applicable.
- Install the rocker arm covers.
- Run the engine and check for leaks/proper operation.