Oil Relief Valve; Removal Of Cylinder Assembly; Assembly Of Cylinder Assembly - Lycoming O-290 Operator's Manual

SECTION 5
MAINTENANCE PROCEDURES
e. Oil Relief Valve (Adjustable) – The adjustable oil relief valve enables the operator to maintain engine
oil pressure within the specified limits. If the pressure under normal operating conditions should
consistently exceed the maximum or minimum specified limits, adjust the valve as follows:
With the engine warmed up and running at approximately 2000 RPM, observe the reading on the oil
pressure gage. If the pressure is above maximum or below minimum specified limits, stop engine and
screw the adjusting screw out to decrease pressure and in to increase pressure. Depending on
installation, the adjusting screw may have only a screw driver slot and is turned with a screw driver;
or may have the screw driver slot plus a pinned .375-24 castellated nut and may be turned with either
a screw driver or a box wrench.
4. CYLINDER ASSEMBLY. Although the complete procedure for disassembly and reassembly is given here,
it is recommended that, as a field operation, cylinder maintenance be confined to replacement of the entire
assembly. Valve replacement should be undertaken only as an emergency measure.
a. Removal of Cylinder Assembly –
(1) Remove exhaust manifold.
(2) Remove rocker box drain tube, intake pipe, priming lines and any clips that interfere with the
removal of cylinder.
(3) Disconnect ignition cable at spark plugs and remove spark plugs. Remove rocker box cover and
rotate crankshaft until piston is approximately at top center of the compression stroke.
(4) Remove valve rockers by sliding the valve rocker shaft aside enabling the valve rockers to be
removed. Valve rocker shaft can be removed when the cylinder is taken from the engine.
(5) Remove push rods by grasping the ball end and pulling rod out of shroud tube.
(6) Remove cylinder base nuts and pull cylinder directly away from the crankcase. Do not allow the
piston to drop against the crankcase as the piston leaves the cylinder. Hold shroud tubes to prevent
their falling.
The tappets, push rods, rocker arms and valves must be identified so that they can be
assembled in the same location from which they were removed.
b. Removal of Valves and Valve Springs from Cylinder – Place the cylinder over a block of wood so as to
hold the valves in a closed position. Compress the valve springs using the valve spring compressor.
Remove the split keys from the end of the valve stem. The valve springs and valve spring seats may
now be removed from the cylinder head. Hold the valve stems so that the valve will not fall out and
remove the cylinder from the holding block. The valves may now be removed from the inside of the
cylinder.
c. Removal of Piston from Connecting Rod – Remove the piston pin plugs. Insert piston pin puller
through piston pin, assemble puller nut; then proceed to remove piston pin. Do not allow connecting
rod to rest on cylinder pad of the crankcase. Support with heavy rubber bands, discarded cylinder base
oil ring seals or any other method.
5-6
LYCOMING OPERATOR'S MANUAL
NOTE
O-235 AND O-290 SERIES