compression. Engines having cylinders with below
minimum required compression will be processed using
the following procedures.
Remove rocker box covers on
cylinders with low compression.
Turn crankshaft until piston is on
top dead center of compression stroke and check intake
and exhaust valves for clearance.
When valves are held open due to
negative clearance, adjust valves to proper clearance.
Check for excessive leakage past
piston by squirting engine oil into cylinder, pulling engine
Continue cylinder In service if
compression Is up to required minimum.
Cold cylinder check. The tendency
for any cylinders to be cold or only slightly warm indicates
lack of combustion or incomplete combustion within the
cylinder. Perform this check using an approved cold
Head aircraft into wind to minimize
irregular cooling of Individual cylinders.
Open cowl flaps.
Do not close cowl flaps under any
circumstances, as the resulting heat
will affect the readings obtained and
overheat the ignition leads.
Start engine. After engine is
running, place ignition switch to position where excessive
rpm drop is obtained. In cases where an excessive rpm
drop has occurred on both magnetos, or where excessive
manifold pressure is obtained at a given rpm, perform
check twice, once on LEFT and once on RIGHT position.
Operate engine at roughest speed
between 1200 and 1600 rpm or at rpm up to Ignition
check speed until a cylinder head temperature reading
of 302 to 338°F (150 to 170°C) is obtained or until
temperature stabilizes at a lower reading.
In cases where engine roughness is
encountered at more than one
speed, or there is an indication that
a cylinder ceases to operate at idle
speed or higher speeds, it will be
desirable to run engine at each of
these speeds and perform a cold
cylinder check to pick out all dead
In cases where lower output or
engine vibration is encountered at
speeds above 1600 rpm, when
operating with ignition switch on
BOTH, engine should be run at the
encountered until cylinder head
temperature reaches 302 to 338 °F
(150 to 170C), or until temperature
has stabilized at a lower value.
Stop engine by moving mixture
control to IDLE CUT-OFF position When engine ceases
firing, turn off both individual and master Ignition
temperatures of each cylinder, starting with any cylinder
and proceeding In numerical order around engine, by
pressing tip of Indicator pickup rod of cold cylinder tester
against each cylinder.
It is essential that a firm contact be
made at the same relative location on
temperature value This measurement
must be performed in the shortest
possible time after engine ceases firing.
Recheck cylinders that have low
values and two cylinders having highest readings to
determine amount of cooling during check.
obtained In order to determine which cylinders are dead
or operating intermittently.