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 buildup.
- Remove the valve keepers, retainer, spring shield (if equipped) and valve spring using a valve spring compressor (the locking C-clamp type is the easiest to use).
- Do not mix removed parts. Place the parts from each valve in a separate container, numbered and identified for the valve and cylinder.
- 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 stick in case the numbers marked on the valve head gets rubbed off.
- 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 build-up will have to be chipped away. Use a blunt pointed drift for carbon chipping, be careful around valve seat areas.
When using a wire brush to clean carbon on the valve parts, valves, etc., be sure the deposits are actually removed, rather than burnished.
- Use a 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 blunt drift.
- Wash and clean all valve springs, keepers, retaining caps, etc., in safe solvent. Remember to keep parts from each valve separate.
- Check the cylinder head for cracks. Cracks usually start around the 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 a 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 and/or valve stem. If a dial indicator is on hand, mount the indicator so that gauge stem is 90° to the valve stem as close to the top of the valve guide as possible. Move the valve from 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 is causing excessive clearance.
- The valve guide, if worn, must be repaired before the valve seats can be resurfaced. A new valve guide should be installed or, in some cases, knurled. Consult the automotive machine shop.
- Valve faces and valve seats should be machined to specifications: the machine shop can handle the job for you. Only enough material to clean up any pits or grooves should be removed. The valve seat should not be too wide or too narrow. The valve face should contact the seat on their respective centers. The valve seat can be narrowed or widened as required.
- After the valves and valve seats have been machined, they should be hand lapped. 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 face against the seat with the valve stick. Remove the valve and clean the compound from the valve face and seat. If the contact ring is too close to the outer edge of the valve face, narrow the seat: if too close to the inner edge widen the seat. 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 too much material.
- 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.
- Assemble the head using new valve stem guide seals. Lubricate the valve stems before installation. Check the valve spring installed height; shim or replace as necessary.
CHECKING VALVE SPRINGS
Place the valve spring on a flat surface next to a carpenters 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 1.5mm or if the distortion exceeds 1.5mm, replace the spring.
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
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 mounting pad and the base of the spring. Use only washers designed for spring shimming: available at parts houses.
VALVE STEM OIL SEALS
Positive valves seals are used. The seal fits over to top of the valve guide. Always install new valve stem seals when reassembling the cylinder head.