Piper COMANCHE PA-24-180 Service Manual page 298

PIPER COMANCHE SERVICE MANUAL
SECTION VI
POWER PLANT PA-24-180
7-1. Inroduction. This section covers power plants used in the PA-24-180 and is comprised of instructions
for the removal, minor repair. service and installation of the engine cowling. propeller, propeller governor.
engine, engine shock mounts, induction sysem, ignition system and lubrication sysem.
7-2. Desripion.
The PA-24-180 is powered by a Avco-Lycoming 0-360-A four cylinder carburetor
induction. direct drive, wet sump..hozontally opposed air-cooled engine with a compresion ratio of 8.5:1
raced at 180 HP at 2700 RPM and designed to operate on 91/96 (minimum) octane aviation grade fuel.
Cowling completely encloses the engie and consists of an upper and lower section. Side panels lift up
to allow access to the engine.
The propeller may be a constant speed McCauley or HarteUl unit controlled by a governor mounted on
the engine supplying oil through the propeller shaft at various pressures. Oil pressure from the governor
moves the blades into high pitch (reduced RPM) and centrifugal twisting moment of the blades tend to
move them into low pitch (high RPM) m the absence of governor oil pressure.
The induction system consists of a wet type air filter on the early models or a dry type air filter on the
later models and a MA-4-5 Marvel-Schebler carburetor. This engine i normally aspirated with no
restrictions on maximum power output.
Bendix Scintilla S4LN-20 series and S4LN-200 series mgnetos are installed with their associated
components. The S4LN-20 series magneto incorporate a single breaker and an impulse couping installed on
the left magneto. The S4LN-200 series magneto system conusts of a single contact magneto on the right
side of the engine and a dual contacr magneto on the left to obtain the retard spark necessary for saring.
A starting vibrator, magneto switches and sarer switch complete the system.
In addition ro the previously mentioned components, each engine is furnished with a 12-volt starter,
35-ampere or 50-ampere 12-volt generator, vacuum pump drive and fuel pump.
The lubrication system is of the pressure wet sump type. The oil pump which is located in the
accessory housing, draws oil through a drilled passage leading from the oil suction screen located in mn
sump. The oil from the pump then enters a drilled passage n the accessory housing, which feeds me oil to a
threaded connection on the rea face of the accessory housing. where a flexible line leads the oil to the
external oil cooler. Pressure oil from the cooler returns to a second threaded connection on the accessory
housing from which point a drilled passage conducts oil to the oil pressure screen or filter. In the event that
cold oil or an obstruction should restrict the oil flow to the cooler, an oil by-pus valve is provided to pass
the oil directly from the oil pump to the oil pressure screen or filter.
The oil pressure screen or filter element, located on the accessory housing is provided as a means to
filter from the oil any solid particles that may have pased through the suction screen m the sump. After
being filtered in the pressure screen or filter. the oil is fed through a dnlled passage to the oil pressure reliei
valve, located in the upper ngnt side of the crankcse in front of the accessory housing
This relief valve regulates the engine oil pressure by allowing excessive oil to return to the sump. while
the balance of the pressure oil Ls fed to ne main oil gallery in the right half of the crankcase. Residual oil is
returned by gravity to the sump where, after passing through a screen, it i again crculated through the
engine.
POWER PLANT
ISSUED: 8/18/72
2A12