d. Removal of seized spark plugs in the cylinder may be accomplished by application of liquid carbon
dioxide by a Conical metal funnel adapter with a hole at the apex just large enough to accommodate the funnel of
a CO
2
adapter is placed over and around the spark plug. Place the funnel of the CO
2
bottle inside the funnel adapter and
release the carbon dioxide to chill and contract the spark plug. Break the spark plug loose with a wrench.
A warm cylinder head at the time the carbon dioxide is applied will aid in the removal of an excessively seized
plug.
e. Do not allow foreign objects to enter the spark plug hole.
8-39. INSPECTION AND CLEANING OF SPARK PLUG.
a. Visually inspect each spark plug for the following non-repairable defects.
1. Severely damaged shell or shield threads nicked up, stripped or cross threaded.
2. 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 50% 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 .018 of an
inch only.
8-40. 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.
8-41. LUBRICATION SYSTEM. (ENGINE).
8-42. OIL PRESSURE RELIEF VALVE. Subject engines may be equipped with either an adjustable or
nonadjustable 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 STD425 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-PAS VALVE, whose function is to
permit pressure oil to by-pass the oil cooler in case of an obstruction.
PIPER AIRCRAFT
PA-28-161 CADET
AIRPLANE MAINTENANCE MANUAL
Issued: FEBRUARY. 28, 1989
POWER PLANT
1K11