a. Removal/installation
b. Disassembly/reassembly
c. Inspection
– Valve spring free length
Measure the free length of the valve springs.
Replace the springs if they are shorter than the service limit.
– Valve seat width
Measure the valve seat width.
If the valve seat width is under the standard, or over the service limit, recondition the valve seat (P. 9-7).
– Cylinder head
Remove carbon deposits from the combustion chamber.
Clear off any gasket material from the cylinder head surface.
Check the spark plug hole and valve areas for cracks.
Check the cylinder head for warpage with a straight edge and a feeler gauge.
– Valve stem O.D.
Inspect each valve for face irregularities, bending or abnormal stem wear. Replace the valve if necessary.
Measure and record each valve stem O.D.
Replace the valves if their O.D. is smaller than the service limit.
– Valve guide I.D.
Note
Measure and record each valve guide I.D.
Replace the guides if they are over the service limit (P. 9-6).
– Guide-to-stem clearance
Subtract each valve stem O.D. from the corresponding guide I.D. to obtain the stem-to-guide clearance.
If the stem-to-guide clearance exceeds the service limit, determine if the new guide with standard dimensions would bring the clearance within tolerance. If so, replace any guide as necessary and ream to fit. If the stem-to-guide clearance exceeds the service limit with new guides, replace the valves as well.
d. Valve guide replacement
1) Chill the replacement valve guides in the freezer section of a refrigerator for about an hour.
2) Use a hot plate or oven to heat the cylinder head evenly to 150°C (330°F).
Check the temperature with a temperature indicating stick (available at welding supply stores) or equivalent.
3) Remove the heated cylinder head from hot plate and support it with wooden blocks. Drive the valve
guides out of the head from the combustion chamber side.
4) Remove the new valve guides from the refrigerator one at a time as needed.
5) Install the new valve guides from the valve spring side of the cylinder head.
Exhaust side: Drive the exhaust valve guide until the clip is fully seated as shown.
Intake side: Drive the intake valve guide to the specified height (measured from the top of the valve guide, to the cylinder casting as shown).
6) After installation, inspect the valve guide for damage, replace the guide if damaged.
– Valve guide reaming
1) Coat the reamer and valve guide with cutting oil.
2) Rotate the reamer clockwise through the valve guide the full length of the reamer.
3) Continue to rotate the reamer clockwise while removing it from the valve guide.
4) Thoroughly clean the cylinder head to remove any cutting residue.
5) Check the valve guide bore; it should be straight, round and centered in the valve guide. Insert the valve and check operation. If the valve does not operate smoothly, the guide may have been bent during installation. Replace the valve guide if it is bent or damaged.
6) Check the valve guide-to-stem clearance (P. 9-5).
e. Valve seat reconditioning
1) Thoroughly clean the combustion chamber and valve seats to remove carbon deposits.
Apply a light coat of Prussian Blue or erasable felttipped marker ink to the valve face.
2) Insert the valve, and snap it closed against its seat several times. Be sure the valve does not rotate on the seat. The transferred marking compound will show any area of the seat that is not concentric.
3) Using a 45° cutter, remove enough material to produce a smooth and concentric seat.
Turn the cutter clockwise, never counterclockwise.
Continue to turn the cutter as you lift it from the valve seat.
4) Use the 30° – 32° and 60° cutters to narrow and adjust the valve seat so that it contacts the middle of the valve face. The 30° – 32° cutter removes material from the top edge (contact too high).
The 60° cutter removes material from the bottom edge (contact too low). Be sure that the width of the finished valve seat is within specification.
– Valve seat width
5) Make a light pass with 45° cutter to remove any possible burrs at the edges of the seat.
6) After resurfacing the seats, inspect for even valve seating. Apply Prussian Blue compound or erasable felt-tipped marker ink to the valve faces. Insert the valve, and snap it closed against its seat several times. Be sure the valve does not rotate on the seat.
The seating surface, as shown by the transferred marking compound, should have good contact all the way around.
7) Lap the valves into their seats, using a hand valve lapper and lapping compound (commercially available).
