TRUCK SERVICE MANUAL
ENGINE
Table 14-3: Injection Timing
Piston
Travel
Push Tube Travel (Inches)
Engine Model
(Inches)
Nominal
Fast
Slow
NT-855-310 (All) NT-855 Series
-0.2032
-0.0360
-0.0340
-0.0380
b. Recheck indicator positioning. Be sure indicators are
not bottoming or binding.
c. Carefully recheck top center position. Be sure each
step is carried out as described.
7. If push tube travel is greater than limits indicated in
Table 14-3, engine timing is slow; if push tube travel is
less, timing is fast. Injection timing may be advanced or
retarded by adding or removing cam follower gaskets.
Remove gasket on right hand engine to retard timing.
Add gaskets on left hand engines to retard timing.
Note: If required, an extra-thick gasket should be used
when needed instead of several thin gaskets.
Injectors
1. Lubricate the injector body "O" rings with light coat of
clean lubricating oil.
Fig. 148, (Ni1432). injection timing procedure
2. Start the injector assembly into bore, from intake side
3. Bar crankshaft in rotating direction (2) until piston
of engine, injectors are to be placed with filter screen at
follower rod top is opposite 90 deg. ATC mark on timing
twelve o'clock, guide by hand until injector is aligned.
tool. At this point, position push tube indicator on push
rod follower to about 0.020 inch from its inner travel stop.
3. Place ST-448 Valve Spring Compressor on top of
Zero indicator dial at this point.
injector plunger coupling and "seat" injector by giving a
4. Bar crankshaft opposite rotating direction (3) to
quick, hard push.
position piston follower rod at 45 deg. BTC.
Note: Both indicators move in same direction when
4. Place hold-down plate over injector body with
cylinder is on proper stroke. If push tube indicator does
counterbore up. Start hold-down capscrews. Do not
not move same direction as piston indicator, bar
tighten.
crankshaft one complete revolution to place cylinder on
5. Carefully insert injector plunger link. Torque hold-
5. Bar crankshaft in direction of rotation until piston
down capscrews to 11 to 12 ft-lbs [1.5 to 1.7 kg ml in 4
follower rod is almost in contact with indicator stem.
ft-lb [0.6 kg m] increments.
Gently move crankshaft to position piston indicator to
0.0032 inch before 0. This position is actually 0.2032
Fuel Fittings And Lines Coat fuel fittings with sealer.
inch before 0, since the indicator will have receded (hand
Inlet and drain fittings may be installed either in front of
will have gone around twice) over 0.200 inch as the
No. 1 head or rear of No. 3 head as used. Connect
crankshaft was moved to 45 deg. BTC. Since exact
tubing to appropriate fitting.
reading in ten-thousandths must be estimated, exercise
care in bringing piston travel indicator to reading.
VALVE CROSSHEAD ADJUSTMENT
6. Read push tube travel indicator. It should read the
number of thousandths before zero that is called for in
1. Position crossheads over guides with adjusting screw
Table 14-3. Notice that a range of about 0.004 inch is
toward water manifold. Loosen adjusting screw locknut,
within specification.
back adjusting screw off one turn.
Note: Never make a change in cam follower gaskets for
timing purposes before making following checks:
Note: Engines using Jacobs Brake use special
a. Be sure cam follower housing capscrews are
crossheads on exhaust side of head. See Group 20.
tightened to 30 to 35 ft-lbs [4.1 to 4.8 kg ml torque.
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