Piper Comanche PA-24 Service Manual page 413

7-1. Introduction.
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 system, ignition system and lubrication system.
7-2. Description.
The PA-24-180 is powered by a Lycoming 0-360-A four cylinder carburetor induction, direct drive, wet
sump, horizontally opposed air-cooled engine with a compression ratio of 8.5:1 rated at 180 HP at 2700
RPM and designed to operate on 91/96 (minimum) octane aviation grade fuel.
Cowling completely encloses the engine 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 Hartzell 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 movement of the blades tend to
move them into low pitch (high RPM) in 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 is normally aspirated with no
restrictions on maximum power output.
Bendix Scintilla S4LN-20 series and S4LN-200 series magnetos are installed with their associated
components. The S4LN-20 series magneto incorporates a single breaker and an impulse coupling
installed on the left magneto. The S4LN-200 series magneto system consists of a single contact magneto
on the right side of the engine and a dual contact magneto on the left to obtain the retard spark necessary
for starting. A starting vibrator, magneto switches and starter switch complete the system.
In addition to 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 the sump. The
oil from the pump then enters a drilled passage n the accessory housing, which feeds the oil to a
threaded connection on the rear 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-pass 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 passed through the suction screen in the sump. After
being filtered in the pressure screen or filter, the oil is fed through a drilled passage to the oil pressure
relief valve, located in the upper right side of the crankcase 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 is fed to the 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 is again circulated through the
engine.
04/01/09
PIPER COMANCHE SERVICE MANUAL
SECTION VII
POWER PLANT PA-24-180
2A11
VII - POWER PLANT
(PA-24-180)