(2) Place the collet of tool inside the valve seat
c. Inspect Exhaust Valve Spring.
insert so the bottom of the collet is flush with the
(1) Inspect spring for pitted or fractured coils.
bottom of the insert.
(2) Check the exhaust valve spring to insure a
load of less than 25 pounds will compress the spring
(3) Hold the collet handle and turn the T
handle to expand the collet cone until the insert is
to 1.93 inch.
held securely by the tool.
d. Remove Exhaust Valve.
(1) With the cylinder head removed from the
(4) Insert the drive bar of the tool through the
engine, remove the valve springs as outlined above.
(2) Turn cylinder head over and withdraw the
(5) Tap the drive bar once or twice to move the
insert about 1/16 inch away from its seat in the
e. Inspect Exhaust Valves.
(1) Clean the exhaust valve with fuel oil.
(6) Loosen the collet cone and move the tool
into the insert slightly so the narrow flange at the
(2) Check the valve stem for scratches or scuff
bottom of the collet is below the valve seat insert.
(3) Inspect the valve face. It should be smooth,
(7) Tighten the collet cone and continue to
unpitted and free from ridges or cracks. Carbon on
drive the insert out of the cylinder head.
the face of the valve indicates a faulty seat and a
k. Install Exhaust Valve Seat Insert.
resultant leak (or blow-by).
(1) Clean the valve seat insert counterbores in
the head with trichlorethylene (O-T-236) or other
(4) Inspect the valve head. It should be square
good solvent. Wash the valve seat inserts with the
with the valve stem and should not be warped.
same solvent. Dry with compressed air.
(5) Reface the valve or install a new valve.
Refer to table 1-1.
(2) Inspect the counterbores for cleanliness,
f. Inspect Exhaust Valve Guide.
concentricity, flatness and cracks. The coun-
terbores have a diameter of 1.159 inch to 1.160
(1) After cleaning, inspect the valve guide for
inch and a depth of 0.300 inch to 0.312 inch.
fractures, scoring or excessive wear.
(3) Immerse the cylinder head for at least 30
(2) Check the valve-to-guide clearance. Worm
minutes in water heated to 180° F. to 200° F.
valve guides may eventually result in improper
valve seat contact. If the clearance exceeds 0.005
(4) Rest the cylinder head, bottom side up, on
the work bench and locate the insert squarely in the
inch, replace the valve guides.
counterbore, seating face up. Install the insert in
g. Remove Exhaust Valve Guide.
the cylinder head while the head is still hot and the
(1) Support the cylinder head, bottom side up,
insert is at room temperature, otherwise installation
on wooden blocks at least three inches thick.
may be difficult and the parts may be damaged.
(2) Drive the valve guide out of the cylinder
(5) Drive the insert in place with the installing
tool until it seats solidly in the cylinder head.
h. Install Exhaust Valve Guide.
(6) Grind the valve insert and check it for
(1) Insert the threaded end of the valve guide
into the installing tool.
concentricity in relation to the valve guide.
(2) Locate the valve guide squarely in the
l. Recondition Exhaust Valve and Valve Seat
cylinder head and tap gently to start it into place.
Insert. An exhaust valve which is to be reused may
(3) Drive the guide in until the tool contacts
be refaced, if necessary. To provide sufficient valve
the bottom of the counterbore. Refer to table 1-1.
strength and spring tension, the edge of the valve
head must not be less than 1/32 inch thick. Before
Do not use the valve guide as a means of
either a new or used valve is installed, examine the
turning the cylinder over or in handling
valve seat insert in the cylinder head for proper
the cylinder head.
valve seating. The proper angle for the seating face
i. Inspect Exhaust Seat Insert.
of both the valve and valve seat insert is 30°. The
(1) Inspect the valve seat inserts for excessive
angle of the valve insert must be exactly the same as
wear, pitting or cracking.
the angle of the valve face to provide proper seating
of the valve. When a new valve seat insert is in-
(2) Inspect the valve seat insert for improper
seat angle. The proper angle for the seating face of
stalled, or an old insert is reconditioned, the work
both the valve and the insert is 30°
must be with a grinding machine. Grind the inserts
j. Remove Exhaust Valve Seat Insert. The valve
seat inserts are pressed into the cylinder head and,
(1) First apply the 30° grinding wheel on the
therefore, must be removed as outlined in the
valve seat insert.
following procedure to avoid damage to the
(2) Use the 60° grinding wheel to open the
throat of the insert.
(1) Place the cylinder head on its side on the
(3) Grip the top surface of the insert with the
15° wheel to narrow the width of the seat to the