TM 5-3810-289-34
Figure 3-155. Pencil marks on valves.
Figure 3-156. Reaming valve guide.
(b) Ream valve guides with proper reamer
to dimensions shown in table 2-2.
Caution: Special care must be used to avoid
breaking carbide tips. Sharpen tipped tools on a
diamond-impregnated wheel.
d. Replacement.
(1) Install new guides with arbor press and
ST 740 valve guide drive, figure 3-157.
(2) If proper valve guide mandrels are not
available, press guides into head to obtain protrusion
above head surface as listed in table 2-2.
(3)
Most valve guides will not require
reaming. Insert valve into guide and check for freedom
of movement, or check guide with small bore gage to
determine if guide bore is too small.
Caution: Guides which have been specially
treated, identified by a dull grey appearance, are not
to be reamed.
Figure 3-157. Valve
(4) Insert valves.
(5) Place cylinder head face down on a
3-32. Tappets and Tappet Guides
wooden bench or protective surface to prevent marring
a.
General.
Tappets are used to transmit
milled surface.
movement from the engine camshaft to the push tubes
(6) Assemble lower valve spring guides on
and rocker levers to actuate the injectors and valves.
valve guides.
Tappet assembly is made up of a body containing a push
(7) Assemble springs.
tube seat, a roller and pin; the roller rides on the
Note. Use same part number spring with mating
camshaft lobe.
spring under crosshead.
b. Removal.
Note. Reground valve heads seat deeper in
(2) Using a wire with a hook on one end,
cylinder head causing valve stem to protrude further
hook wire into tappet guide slot tappet
above the guide. This allows valve spring to extend
nearest the outside wall of block) and lift tappets
beyond length limits and causes weak spring action.
former engine.
Therefore, up to 1/16 in. of spacers may be used to
c. Disassembly.
reduce valve spring length.
(1) Refer to figure 3-159 and disassemble
Caution: Too many spacers will cause the
the tappet assembly.
compressed spring to become a solid sleeve, see
(2) Place 0.006 in. shim between tappet
and side of roller to prevent spring for k when removing
(8) Assemble upper valve spring guide.
roller: press on end of pin that is not lock-wired
(9) Use ST448 Valve Spring Compressor to
(pinned)..
compress valve spring. Insert new half-collets.
(10) Insert new locks.
3-56
