GMC 4000 Series Service Manual page 307

Sec. 6B
Page 296
TORO-FLOW DIESEL ENGINE
Figure 6 — Firing O rd e r a n d M a te d
C ylind ers for D iesel E n g in e
NOTE: Figure 6 shows firing order for 6-cyl­
inder engines and also indicates pairs of cylinders
in which pistons reach top-dead-center at same
time. Valve springs at any two cylinders having
same letter identification in figure 6 may be chang­
ed without turning crankshaft.
Exhaust Valve
Cylinder Head
Valve Rotator
Spring Cap
Valve Keys
Outer Springs
Figure 7 — Cross Sectional V ie w of C ylinder H ead
G M C S E R V I C E M A N U A L
0.050" M A X .
Inner Springs
Intake Valve Oil Seal
9
Intake Valve
10
Exhaust Valve Seat
Insert
5. Referring to figure 7 assem ble rotator (if
removed), inner and outer springs, and spring cap,
then use compressor tool to force springs and cap
down far enough to permit installation of valve
keys.
6. On intake valve install oil seal (8, fig. 7).
Place valve keys (5, fig. 7) in valve stem groove,
then remove spring com pressor.
7. Install rocker arm and shaft assembly fol­
lowing instructions given later under "Valve Oper­
ating Mechanism Replacement."
8. Install rocker arm cover; start engine and
operate until warmed up to normal operating temp­
erature. Check and adjust valve lash if necessary.
M ANIFO LD REPLACEMENT
The intake and exhaust manifolds (fig. 8) are
attached to cylinder heads by same clamps and
b o lts. A continuous strip type gask et is in sta lle d
between cylinder head and manifolds.
REMOVAL
1. Remove from cab access covers (when
used) and other equipment which may interfere
with manifold removal. On tilt cab models, tilt the
cab for access.
2. Disconnect air intake hoses from intake
manifolds.
3. Disconnect exhaust pipes from exhaust
manifolds.
4. Remove clamp bolts and clamps. Remove
end bolts and washers, then remove manifolds and
gaskets.
INSTALLATION
1. Clean the gasket surfaces on manifolds and
mating surfaces on cylinder heads.
2. Locate manifolds and new gaskets and in­
stall end bolts with washers. Do not tighten end
bolts until clamps and clamp bolts have been start­
ed. Tighten all bolts to apply even pressure at gas­
kets. Correct torque for intake manifold end bolt is
20 foot-pounds, exhaust manifold end bolt 20 foot­
pounds, and all manifold clamp bolts 20 to 25 foot­
pounds.
ROCKER A R M COVER
REPLACEMENT
REMOVAL
NOTE: On some tilt cab models, it is neces­
sary to remove transm ission shift rods to permit
left-hand rocker arm cover removal.
1. Remove crankcase ventilation hoses (when
used) from covers.