REMOVAL & INSTALLATION
See Figures 1 through 5
- Place the head on its side, on blocks of wood 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 buildup.
- Using a valve spring compressor (the locking C-clamp type is the easiest kind to use) compress a valve.
- Remove the valve keepers, retainer, spring shield and valve spring.
- 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 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 wood valve holding stick.
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 wires 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 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 similar method, have check performed 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 slight 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 degrees 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.
- Have the valves and valve seats refaced. The valve seats should be a true 45 degrees 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 degrees grinding wheel to remove material from the bottom of the seat for raising and a 30 degrees 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. 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 degrees. Remove only enough metal to clean up the valve face or to correct runout. If the edge of a valve head, after machining, is 1 / 32 inch; (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 inch; (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.
- Install new valve stem oil seals (and install exhaust metal caps if so equipped).
- Using a valve spring compressor (the locking C-clamp type is the easiest kind to use), install the valve keepers, retainer, spring shield and valve spring .
- Check the valve spring installed height, shim or replace as necessary.
CLEANING AND INSPECTION
See Figures 6 and 7
- With the valves installed to protect the valve seats, remove deposits from the combustion chambers and valve heads with a scraper and a wire brush. Be careful not to damage the cylinder head gasket surface. After the valves are removed, clean the valve guide bores with a valve guide cleaning tool. Using cleaning solvent to remove dirt, grease and other deposits, clean all bolts holes; be sure the oil passage is clean (V8 engines).
- Remove all deposits from the valves with a fine wire brush or buffing wheel.
- Inspect the cylinder heads for cracks or excessively burned areas in the exhaust outlet ports.
- Check the cylinder head for cracks and inspect the gasket surface for burrs and nicks. Replace the head if it is cracked.
- On cylinder heads that incorporate valve seat inserts, check the inserts for excessive wear, cracks, or looseness.
When the cylinder head is removed, check the flatness of the cylinder head gasket surfaces.
- Place a straightedge across the gasket surface of the cylinder head. Using feeler gauges, determine the clearance at the center of the straightedge.
- If warpage exceeds 0.003 inch; (0.076mm) in a 6 inch; (152mm) span, or 0.006 inch; (0.152mm) over the total length, the cylinder head must be resurfaced.
- If necessary to refinish the cylinder head gasket surface, do not plane or grind off more than 0.254mm (0.010&inch;) from the original gasket surface.
When milling the cylinder heads of V6 or V8 engines, the intake manifold mounting position is altered, and must be corrected by milling the manifold flange a proportionate amount. Consult an experienced machinist about this.
See Figure 8
The valve must be lapped into their seats after resurfacing, to ensure proper sealing. Even if the valves have not been refaced, they should be lapped into the head before they are installed.
Set the cylinder head on the workbench, combustion chamber side up. Rest the head on wooden blocks on either end, so there is 2-3 inch; (51-76mm) between the tops of the valve guides and the bench.
- Lightly lube the valve stem with clean engine oil. Coat the valve seat completely with valve grinding compound. Use just enough compound so that the full width and circumference of the seat are covered.
- Install the valve in its proper location in the head. Attach the suction cup end of the valve lapping tool to the valve head. It usually helps to put a small amount of saliva into the suction cup to aid it sticking to the valve.
- Rotate the tool between the palms, changing position and lifting the tool often to prevent grooving. Lap the valve in until a smooth, evenly polished seat and valve face are evident.
- Remove the valve from the head. Wipe away all traces of grinding compound from the valve face and seat. Wipe out the port with a solvent soaked rag, and swab out the valve guide with a piece of solvent soaked rag to make sure there are no traces of compound grit inside the guide. This cleaning is very important, as engine scoring and damage will result if any grit is remaining when started.
- Proceed through the remaining valves, one at a time. Make sure the valve faces, sets, cylinder ports and valve guides are clean before reassembling the valve train.