Piper COMANCHE PA-24-180 Service Manual page 328

PIPER COMANCHE SERVICE MANUAL
7-52. Installation Of Spark Plugs. Before installing spark plugs, ascertain that the threads within the
cylinder are clean and not damaged.
a. Apply anti-seize compound sparingly on the threads and install gasket and spark plugs. Torque 360
to 420 inch pounds.
CAUTION
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.
7-53. Lubrication System.
7-54. 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.
Non-adjustable Oil Pressure Relief Valve - The valve is not adjustable; however, the pressure can be
controlled by the addition of a maximum of three STD-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 pressure oil to
by-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 No. 3 cylinder. If the pressure under normal
operating conditions should consistently exceed 90 psi., or run less than 60 psi., adjust the valve as follows:
With the engine thoroughly warmed up and running at a maximum of 2200 RPM, observe the reading
on the oil pressure gauge. If the pressure is above 90 psi, stop engine, loosen the adjusting locknut; and back
off the adjusting screw one or two full turns. Tighten locknut and retest. If pressure is too low, turn
adjusting screw further into the relief valve plug, thereby increasing the tension on the relief valve spring.
When the valve has been satisfactorily adjusted, tighten the locknut and lock wire the crown nut to the
drilled ear projecting from the valve mounting boss.
7-55. Oil Screens. The oil screens are the pressure screen, located in a dome shaped housing, above and
between the magnetos and the suction screen located in the lower aft section of the sump. These screens
should be cleaned at each oil change to remove any accumulation of sludge and to examine for metal filings
or chips. If metal particles are found in the oil screens, the engine should be examined for internal damage.
POWER PLANT
ISSUED: 8/18/72
2B18