Cylinder Heads - Onan T260G Service Manual

CYLINDER HEADS
,Remove the cylinder heads for lead cleaning and
gasket change at least every 250 hours, or when poor
engine performance is noticed.
1.
Use a 1/2 inch (13 mm) socket wrench to remove
Do not torque or remove heads
when they are hot. Warpage
may occur. The gasket surface must be below
100" F before removal. At temperatures above
100" F, the gasket will become gummy and diffi-
cult to remove from the surface of the block and
cylinder head.
cylinder head nuts. Lift heads off.
CAUTION
2. After removing heads, clean out all carbon depos-
its. Be careful not to damage the outer sealing
edges where gaskets fit. The heads are made of
aluminum and can be damaged by careless
handling.
3. Use new head gaskets and clean both the heads
and thecylinder block thoroughly where the head
gaskets rest.
4. Place a head gasket on the cylinder head and
align the stud holes in the gasket with the stud
holes in the cylinder head. While holding the
gasket against the cylinder head, carefully install
the cylinder head on the engine. Do not attempt
to slide the gasket over the studs without the
cylinder head behind it or the gasket may tear.
5. Install a flat washer, two compression washers,
and nut on each of the top six studs(see Figure 28
for correct sequence). When properly installed,
only the outside edges of the compression wash-
ers will be in contact with each other. Install a flat
washer and nut on each of the four bottom studs.
f -
COMPRESSION
WASHERS
HEAT TREATED
.HARDENED
WASHERS
HEAD
GASKET
6. Follow the head torque sequence shown in Fig-
ure 29 tightening all nuts to 5 ft-lbs (7 Nm), then
10 ft-lbs (14 Nm), then to the torque specified in the
ASSEMBLY TORQUESsection. Recheck all nuts for
correct torque.
LEFT CYLINDER RIGHT CYLINDER
FIGURE
29.
HEAD BOLT TIGHTENING SEQUENCE
CAUTION
Too much torque will flatten the
compression washers and could
result in engine damage.
7. Recheck torque before engine has run a total of
50 hours.
CAUTION
Do not torque or remove heads
when they are hot. Warpage
may occur. The gasket surface must be below
100F before removal. At temperatures above
100" F, the gasket wlll become gummy and dlffi-
cult to remove from the surface of the block and
cylinder head.
6 LONG STUDS/HEAD
4
SHORT STUDS/HEAD
FIGURE 28. CYLINDER HEAD WITH COMPRESSION
WASHERS