Piper PA-24 Comanche Service Manual page 385

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PIPER COMANCHE SERVICE
MANrAL
7A-81. Inspection And Cleaning Of Spark Plug.
a. Visually inspect each spark plug for the following non-repairable defects:
I. Severely damaged shell or shield threads nicked up. stripped or crossthreaded .
., Badly battered or rounded shell hexagons.
3.
Out-of-round or damaged shielding barrel.
4.
Chipped. cracked. or broken ceramic insulator portions.
5.
Badly eroded electrodes worn to approximately 50C( of original
size.
b. Clean the spark plug as required. removing carbon and foreign deposits.
c. Test the spark plug both electrically and for resistance.
d. Set the electrode gap at .015 to .018 of an inch or if a smoother operation at idle speed and reduced
magneto drop-off is desired. set at .018 to .022 of an inch. However. with wide gap setting the plugs must be
serviced at more frequent intervals. Fine wire platinum or iridium electrodes should be set at .015
to
.01S of
an inch only.
7A-lQ. Installation Of Spark Plugs. Before installing spark plugs. ascertain that the threads within the
cvlinder are clean and not damazed.
. a.
Apply anti-seize
compound
sparingly on the threads and install gasket and spark plugs. Torque
360
to .t10 inch pounds.
CAUTIO~
Make
certain the deep socket is properly seated on the spark plug
hexagon as damage to the plug could result if the wrench is cocked to
one side when pressure is applied.
b. Carefully insert the terminal insulator in the spark plug and tighten the coupling nut.
7A-S3. Lubrication
System,
".-\-84. Oil Pressure Relief Valve. Subject engines may be equipped with either an adjustable or non-
adjustable oil pressure relief valve. A brief description of both types follows:
a. :\on-adjustable Oil Pressure Relief Valve: The valve is not adjustable: however. the pressure can be
controlled by the addition of a maximum of three STO-425 washers under the cap
to
increase pressure or
the use of a spacer (Lycoming P N 73629 or 73630) to decrease pressure. Particles of metal or other foreign
matter lodged between the ball and seat
will result in a drop in oil pressure. It is advisable. therefore to
disassemble. inspect. and clean the valve if excessive pressure fluctuations are noted. The oil pressure relief
valve is
not to be mistaken for the oil cooler
by-pass
valve. whose function is to permit
pres-ure
oil to
hy-pass the oil cooler in case of an obstruction.
b. Adjustable Oil Pressure Relief Valve: The adjustable oil pressure relief valve enables the operator
to maintain engine oil pressure within the specified limits (refer to the engine manufacturer's appropriate
manual).
The
valve
is located above and to the rear of :\0.5 cylinder. If the pressure under normal operating
conditions should consistently exceed 90 psi. or run less than 60 psi. adjust the valve as follows:
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ISSl'EO:
8/18/72
2E5
POWER PLA:"IT