Engine Overhaul Manual
Jabiru Aircraft
Pty Ltd
Jabiru 2200 & 3300 Aircraft Engines
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Dated : 28/10/2014
Issued By: AS
Page: 142 of 201
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7.8.10 Cylinder Heads
The cylinder heads must be fitted to the engine in a sequence as the rocker shafts are installed in-situ.
The recommended sequence is: fit an upper head
– say 5 or 6 for a 3300 engine – first, then work
downwards, completing each head assembly in turn.
For each head the following sequence must be followed:
1. The outer bottom circumference edge of the hydraulic lifter should be lightly polished to remove any
burrs or sharp edges.
2. For hydraulic lifter engines, fill the lifters with oil (using an oil can - Figure 178) and fit the lifters to
the crankcase. The outside of the lifter must also be well lubricated with oil before fitting and note
also the light covering of grease which has been applied to the camshaft lobes
– this is to minimise
wear during initial start-up. Note that solid lifter engines have their lifters fitted before crankcase
assembly
– there is no way to do it once the case halves are assembled.
3. For engines equipped with roller cam followers the follower locking plates must be installed now
–
see Figure 179. This plate should be a neat fit with a small amount of clearance from the lifter. It
may be necessary to lightly linish the plates before installing to remove sharp edges etc. Note the
orientatio
n of the plate when installed: the two “legs” on the plate must point out of the case.
4. Fit new O rings to the crankcase to seal the pushrod tubes (solid lifter models)
– see Figure 178.
5. For hydraulic lifter engines, fit new O rings to the pushrod tube adaptors. Again these must be well
lubricated with oil or Nulon L90. Fit the adaptors to the crankcase.
6. For roller follower models, the oil return manifolds can be fitted now. Fit new O rings and use a
small amount of Loctite 515 to seal the manifold to the engine. Figure 180 shows the manifolds
installed.
7. Fit the pushrod tubes (2) to the crankcase.
8. If the engine uses an external oil feed pipe this must be fitted between the cylinders. It should be
fitted but the clamps not tightened until all the heads are fitted. For later specification engines which
use the pushrod tubes to feed oil to the rocker gear this step is omitted. Note that if an engine has
been converted from the external oil feed to the new hollow pushrod oil feed it will be necessary to
fit blanking plugs to the old oil feed holes in the sides of the crankcase as shown in Figure 185.
Solid lifter engines must use the external oil feed tube system.
9. Fit the cylinder head to the cylinder, feeding the pushrod tubes into the head
– see Figure 182.
10. Apply high-temperature lubricant to the threads of the cylinder and the cylinder head screws
– these
are susceptible to rust which can lead to inaccurate bolt tension readings later in service. The
lubricant is designed to prevent rust on the threads and to ensure a consistent torque setting during
the engine’s service life. Figure 181 refers.
11. Install the cylinder head bolts and washers with a light tension setting. In particular the lower head
screw (which is accessed via the hole inside the rocker cavity) must be left loose
– the special
washer under this screw can rub against the rocker tubes and so must be carefully positioned to
avoid this. Figure 181 (right) shows this screw being tightened.
12. Using the spring compressor tool shown in Figure 10 and Figure 184, open both valves to allow the
installation of the valve rockers. This step may be bypassed for a solid lifter engine if the overhauler
prefers, but even for those engines this tool makes the assembly simpler by allowing the heads to
be fitted as complete assemblies.
13. Fit the valve rockers, taking care that the pushrod is correctly seated into the sockets in the lifter and
in the rocker. The rockers and the rocker shaft must be lubricated well with Nulon L90 or oil as
shown in Figure 183 and then driven in using a suitable punch and a soft hammer. The shaft is
punched in with the rounded end leading.
14. Fit the rocker shaft locking screw and remove the valve compressor tool.
15. Tighten the cylinder head screws (6) to 15 lb.ft and then to the value specified in Table 9 using a
standard diagonal tensioning pattern.
16. Fit the tapered blanking plug to the access hole for the lower cylinder head screw (shown in Figure
– left). Note that this plug must not be over-tightened. If the plug is done up too tightly then
over time its tapered thread will wear the thread in the cylinder head, requiring it to be screwed in
further and further to be tight. Eventually the thread can be worn so much that the tapered plug will
not lock in. A tension of about 6lb.ft is sufficient for this plug.
