Lycoming AIO-320, Operator'S Manual

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SECTION 5 LYCOMING OPERATOR’S MANUAL
MAINTENANCE PROCEDURES IO-320 SERIES
e. Assembly of Hydraulic Tappet Plunger Assemblies –
To assemble the unit, unseat the ball by inserting
a thin clean bronze wire through the oil inlet hole. With the ball off its seat, insert the plunger and
twist clockwise so that the spring catches.
f. Assembly of Valves in Cylinder –
Prelubricate valve stems with Molytex Grease O or equivalent and
insert each valve stem in its respective valve guide. Place cylinder over a block of wood so that the
valves are held against the seats and assemble the lower valve spring seat, auxiliary valve spring and
outer valve spring over the valve stem and guide. Place the upper valve spring seat on top of the
springs.
NOTE
When installing valve springs, place the dampened end of spring (close wound coils marked
with dye or lacquer) toward the cylinder.
Using a valve spring compressor, compress the valve springs and place the split keys in the groove
around the upper end of the valve stem. Slowly release the pressure on the valve spring compressor
and allow the upper spring seat to lock itself in place around the valve keys.
d. Assembly of Cylinder and Related Parts –
Rotate the crankshaft so that the connecting rod of the
cylinder being assembled is at the top center position that corresponds with both valves closed.
(1) Place each plunger assembly in its respective tappet body and assemble the socket on top of
plunger assembly.
(2) Assemble piston with rings so that the cylinder number stamped on the piston pin boss is toward
the front of the engine. The piston pin should be a hand push fit. If difficulty is experienced in
inserting the piston pin, it is probably caused by carbon or burrs in the piston pin hole. During
assembly, always use a generous quantity of oil, both in the piston hole and on the piston pin.
(3) Assemble one piston pin plug at each end of the piston pin and place a new rubber oil seal ring
around the cylinder skirt. Coat piston and rings and the inside of the cylinder generously with oil.
(4) Using a piston ring compressor, assemble the cylinder over the piston so that the intake and
exhaust ports are at the bottom of the engine. Push the cylinder all the way on, catching the ring
compressor as it is pushed off.
NOTE
Before installing cylinder hold-down nuts, lubricate crankcase thru-stud threads with any
one of the following lubricants, or combination of lubricants.
1. 90% SAE 50W engine oil and 10% STP.
2. Parker Thread Lube.
3. 60% SAE 30W engine oil and 40% Parker Thread Lube.
(5) Assemble hold-down plates (where applicable) and cylinder base hold-down nuts and tighten as
directed in the following steps.
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