REMOVAL & INSTALLATION
- Block the head on its side, or install a pair of head-holding brackets made especially for valve removal.
- Use a socket slightly larger than the valve stem and keepers, place the socket over the valve stem and gently hit the socket with a plastic hammer to break loose any varnish build-up.
- Remove the valve keepers, retainer, spring shield and valve spring using a valve spring compressor (the locking C-clamp type is the easiest kind to use).
- Put the parts in a separate container numbered for the cylinder being worked on; do not mix them with other parts removed.
- Remove and discard the valve stem oil seal; a new seal will be used at assembly time.
- Remove the valve from the cylinder head and place, in order, through holes punched in a stiff piece of cardboard or in a wooden valve holding stick. Number the cardboard or stick in case the number marked on the valve head gets rubbed off.
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.
- 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.
- 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 by another method at a 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 only 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 for raising and a 30° grinding wheel to remove material from the top of the seat to narrow.
- After the valves are refaced by machine, hand lap them to the valve seat. Use valve grinding compound and a small suction cupped valve stick. Place a small amount of compound on the valve face install the valve and rotate the valve, with the stick, back and forth on the valve seat. Clean the grinding compound off and check the position of face-to-seat contact. 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 inch 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 inch.
- After all valve and valve seats have been machined, check the remaining valvetrain parts (springs, retainers, keepers, etc.) for wear. Check the valve springs for straightness and tension.
- Reassemble the head in the reverse order of disassembly using new valve guide seals and lubricating the valve stems. Check the valve spring installed height, and shim or replace the springs as necessary.
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 inch or if the distortion exceeds 1 / 16 inch, replace the spring.
Have the valve springs tested for spring pressure at the installed and compressed height (installed height minus valve lift) using a valve spring tester. Springs should be within one pound, plus or minus, of each other. Replace springs as necessary.Valve Spring Installed Height
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 incorrect, 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
Umbrella type oil seals fitting on the valve stem over the top of the valve guide are used on 6- and 8-cylinder engines. The 4-cylinder engine uses a positive valve stem seal using a Teflon insert. Teflon seals are available for other engines but usually require valve guide machining, consult your automotive machine shop for advice on having positive valve stem oil seals installed.
When installing valve stem oil seals, ensure 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.Valve Seats
If a 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. Consult an automotive machine shop for their advice.Valve Guides
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 the best alternative since a new valve would 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.