REMOVAL & INSTALLATION
See Figures 1 through 18
The diesel has inner and outer springs.
- 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 buildup.
- 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 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 re-install 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 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 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° 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. Chrysler 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 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.
- Valves should be refaced to a true angle of 45°. 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 " (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" (0.254mm).
- Refer to the valve lapping procedure in this section.
- 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 metal caps.
- Install new valve stem oil seals.
- Install 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).
- Check the valve spring installed height, shim or replace as necessary.
After machine work has been performed on the valves, it may be necessary to lap the valve to assure proper contact. For this, you should first contact your machine shop to determine if lapping is necessary. Some machine shops will perform this for you as part of the service, but the precision machining which is available today often makes lapping unnecessary. Additionally, the hardened valves/seats used in modern automobiles may make lapping difficult or impossible. If your machine shop recommends that you lap the valves, proceed as follows:
- Set the cylinder head on the workbench, combustion chamber side up. Rest the head on wooden blocks on either end, so there are two or three inches 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 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 important.
- Proceed through the remaining valves, one at a time. Make sure the valve faces, seats, cylinder ports and valve guides are clean before reassembling the valve train.
CHECKING VALVE SPRINGS
See Figures 19, 20 and 21
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
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.
VALVE SPRING INSTALLED HEIGHT
See Figure 22
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.
Except Diesel Engines
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. Consult an automotive machine shop for their advice.Diesel Engines
Valve seats are replaceable. Special tools are required to remove and install the seats. Considerable care must be exercised when installing the seat inserts. The inserts are installed with a 0.002-0.004" press fit and must be started in place, true with the counterbore in the block. To install the inserts:
- Place the inserts in a container of dry ice for at least 10 minutes.
- Make certain that the block and counterbore are absolutely clean.
- Place the chilled inserts in the counterbore and, using a seat driver, drive the insert in until it bottoms.
If the standard insert is too loose, 0.010" oversizes are available.
- Counterbore the block 0.0035" smaller than the insert to be installed. Run the boring tool down until it bottoms.
Except Diesel Engines
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 answer 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.Diesel Engine
See Figure 23
These guides are replaceable.
- Press out the old guide using tool 31691-10500.
- Press the new guide into the head using tool 31691-00800. Installed height, above the head, should be 17.7-18.3mm.