Piper COMANCHE PA-24-180 Service Manual page 429

PIPER COMANCHE SERVICE MANUAL
7B-50. Inspect on And Cleaing Of Spark Plug.
a. Visually inspect ech spuk plug for the following non-repirable defecs:
1. Severely damaged shell or shield threads nicked up. sripped or crouthreided.
2. Badly battered or rounded shell hexagons.
3. Our-of-round or damaged shielding barrel.
4. Chipped, crcked, or broken ceramic insulator portions.
5. Badly eroded electrodes worn to approximately 50%o ofriginal size.
b. Clean the spark plug u required. removing carbon and foreign deposis.
c. Test hbe spark plug both electrically and for resunce.
d. Set the electrode gap at .015 to .018 of n inch or if a smoother operation at idle speed and
reduced magneto drop-off is desired, ser a .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 .018 of n inch only.
7B-51. Insllation Of Spark F . Before installing spark plugs, ascertain tha the threads within the
cylinder are clean and not dam.u eo
L
Apply anutisize compound sparingly on the threads and instll gaket and spark plugs. Torque 360
to 420 inch pounds.
CAUTION
lake cerrain the deep socker is properly seaed on the spark plug
hexagon s damage to the plug could result if the wrench is cocked to
one side when pressure is applied.
b. Carefully inserr the cerminal insulator in the spark plug and tighten the coupling nut.
7B-52. Lubrication System.
7B-5 3. Oil Relief Valve. The function of the oil pressure relief valve, which i located between the upper
right engine mounting lug and No. 7 cylinder, is to maintain engine oil pressure within specified limits by
withdrawing portion of the oil from the circulating system and returning the oil to the sump should the
pressure become excessive. This valve is not adjustable, however, particles of metal or other foreign mairer
lodged between ball and seat will result n a drop m oil pressure. It is advisable, therefore, to disassemble,
inspect and clan the relief valve if excessve pressure flucruaions are noted.
The oil pressure relief valve is by no means to be confused with the oil cooler by-pass valve, which is
located on the oil pressure screen housing mounting pad. The sole purpose of the by-pass valve is to serve as
a sarety measure. pernutring pressure oil co by-pass the od cooler entrely in case of an obstrucnon within
the cooler
POWER PLANT
ISSUED: 8/18/72
2F23