at the top of insert seat. Thus, for the 30° exhaust
valve face angle and a 1° interference angle, the in-
sert seat grinder wheel must be dressed to grind the
insert seat at an axle of 31°. Likewise, the insert
seat for the intake valve must be ground at 31 . This
is a positive interference angle. A negative angle
must be avoided. The first step in reconditioning a
seat or insert is to grind the seat, removing only
enough metal to produce a pit-free continuous seat.
After the seat has been ground, use a dial gauge to
check concentricity of the seat relative to the valve
guide. The total run-out of a good seat should not
exceed 0. 002 inch total indicator reading.
(3) To determine seat contact in relation to
insert and valve face, wipe a thin film of Prussion
Blue on the valve face and bounce the valve once on the
A thin, continuous line must be evident on
the valve face, otherwise further grinding is required.
Do not revolve valve while checking seat.
(4) The width of the valve seat on both the ex-
haust and service intake inserts is 3/32 inch. If the
seats are too wide or too narrow they must be ground
to the proper width using the appropriate angle grind-
After valves are installed in cylinder head,
make certain the exhaust valve heads are set
in a minimum of 0.053 inch and the intake
valve heads are set in a minimum of 0.054
inch from the cylinder head gasket surface,
otherwise, serious damage will result. If
valve stand -in is less than the allowable
amount, the valve seat must be ground
lower until the allowable stand-in is ob-
e. Rocker Arm, Shaft Inspection and Repair.
(1) Inspect end of rocker arm adjusting screws
and end of rocker arms. If they are worn, the rocker
arm assemblies must be replaced.
(2) Inspect rocker arm shaft bore for wear. The
bore of the rocker arm bore is 0.001 to 0.002 inches
and the outer diameter of the rocker arm shaft is
0.999 to 1.000 inch. The clearance of the rocker arm
shaft to the rocker arm is 0.001 to 0.003 inch and must
not exceed 0. 005 inch. If rocker arm shaft bore is ex-
cessively worn, the rocker arm assemblies must be
Bushings are non-replaceable in rocker
(3) Inspect rocker arm shaft for wear and replace
if necessary. Clean oil holes in rocker arms and rocker
shaft with solvent, Federal Specification P-D-680, a
small wire, and compressed air.
(4) Inspect both ends of push rods for signs of
wear. Polish out nicks or scores.
If pushrods are
bent, twisted, or damaged, replace push rods.
f. Camshaft, Camshaft Gear and Valve Lifter
(1) The outer diameter of all camshaft bearing
journals is 2.130 to 2.131 inches. The inside diameter
of the camshaft bearings, when installed, is 2.133 to
The clearance between the camshaft
journals and bearings is 0.002 to 0.006 inch and must
not exceed 0.008 inch. If exceeded then the bearings
must be replaced.
If the installation of new standard
bearings does not reduce the end clearance to less
than 0. 008 inch, it is recommended to grind the cam-
shaft journals to accommodate 0.010-inch undersize
Likewise, if the journals are worn or
scored to the extent that they will not accommodate
0. 010-inch undersize bearings, the camshaft must be
(2) Inspect the intake and exhaust lobes of the
camshaft for roughness, scoring or excessive wear.
Replace the camshaft if any of these conditions are
found to exist.
(3) Inspect camshaft gear for nicked, scored,
or broken teeth. Replace as necessary.
(4) Inspect thrust plate for wear. Replace if the
wear area is rough or the wear is excessive. New
thrust plate thickness is 0.204 to 0.206 inch.
(5) Inspect valve lifters for excessive wear.
Replace a set of lifters if one or more show excessive
14-79. Reassembly and Installation.
a. Valve Lifter Installation.
(1) Lubricate valve lifters with clean engine oil
and install them in their original positions in the cyl-
(2) Using the wooden dowel method illustrated
in figure 14-40, pull the lifters up so they do not
interfere with camshaft installation.
b. Camshaft and Camshaft Gear Installation.
(1) Place the camshaft in a press with the
shoulder of the first journal resting on parallel bars.
(2) Posit Ion the thrust plate on camshaft.
Change 3 14-85