| Tweet |
Custom Search
|
|
|
||
 (d) Inspect the valve seat for excessive
(2) Install the flywheel housing by reversing the
wear, pitting, cracking, or improper seat angle. Remove a
procedures of removal in step (1) above.
defective seat (para 5-3). Install a new valve seat as follows:
1. Clean the valve seat counterbore
5-7. Valves, Camshaft, and Timing System
with solvent Fed Spec P-D-680. Wash the new valve seat in
a. General. Two exhaust valves are provided for each
the same solvent, and dry both with compressed air.
cylinder. The valves are heat treated and ground to the
2. Inspect
counterbores
for
proper seat angle and diameter.
Each valve stem is
cleanliness, concentricity, and flatness.
Measure the
accurately ground to size, and hardened at the end which
diameter. It should be 1.626 to 1.627 inch diameter, and have
contacts the rocker arm. Valve seat inserts are pressed into
a depth of 0.3705 to 0.3845 inch. The counterbores must be
cylinder head permitting accurate seating valves under
concentric with the valve guides within 0.003 inch total
varying conditions of temperature. Valves and seats are
indicator reading.
ground to a 30 seating angle. Valve springs are held 'in
place by spring caps and tapered two piece locks. Excess oil
from rocker arms lubricates the valve stem ends. Valves are
NOTE
cooled by blower air steam. The camshaft lobes move cam
If required, use valve seats that are
followers, which move push rods against the rocker arms,
0.010 inch oversize on outside
these in turn open the valves and the fuel injector.
diameter.
b. Valves.
(1) Removal. Remove the valves as described in
3. Immerse the cylinder head for at
least 30 minutes in water heated from 185 . to 200 .
F
F
(2) Cleaning, Inspection, and Repair.
4. Rest the warm cylinder head,
(a) Soak
the
valves
(tagged
for
bottom side up, on a work bench and position the seat
identification of port of removal) in clean fuel oil and wipe dry.
squarely in the counterbore, seating face (30 ) up. Install the
Remove stubborn carbon with a sharp hardwood stick. Do
seat while the cylinder head is still warm, and the seat is at
not scratch or scuff stem or face.
room temperature (70 .), otherwise installation will be
F
(b) Inspect the thoroughly cleaned valves
difficult, and the parts may be damaged.
for scuff marks on stem. The faces must be free of ridges,
5. Drive the seat in place with
cracks, or pitting. Replace a defective valve.
installer (table 4-1) until seated solidly in the cylinder head
(c) Clean inside of valve guides with brush
and fuel oil. Inspect guides for fractures, chipping, scoring, or
below.
excessive wear. Check the guide-to valve stem clearance
(use valve removed from the guide), since worn guides result
in improper valve seat contact. If clearance exceeds 0.006
inch, replace the valve guide (para 5-3).
5-29
|
||
|
||
