TEO-540-C1A Engine Maintenance Manual
72-30
© 2018 Avco Corporation. All Rights Reserved
Page 248
November 2018
TEO-540-C1A Engine Maintenance Manual
20.
Heli-Coil
®
Replacement
A.
Replace the spark plug Heli-Coil
®
insert (Figure 49) in the cylinder head if the threads in the
spark plug hole in the cylinder are damaged (usually occurs when hard carbon on the end of
the spark plug causes the insert to unwind during spark plug removal).
Figure 49
Heli-Coils
®
NOTICE:
Always install a larger oversized 0.010 in. (0.254 mm) Heli-Coil
®
insert in the spark
plug hole on the cylinder head to replace a standard sized Heli-Coil
®
insert. Never
replace a standard sized Heli-Coil
®
insert with another standard sized Heli-Coil
®
insert. The oversize Heli-Coil
®
inserts are identified by three marks on the tang of
the Heli-Coil
®
insert as shown Figure 50.
Figure 50
Heli-Coil
®
Inserts for Long Reach Spark Plugs
(1)
Disable all power to the engine to prevent propeller rotation and engine start. Disconnect
ignition leads from all spark plugs.
(2)
If not already done, remove the Heli-Coil
®
insert from the spark plug hole as follows:
(a)
Insert the T-shaped Removing Tool
P/N 64595 (Figure 51) in the spark
plug hole. Press the tool down
firmly for the edge of the tool to cut
into the top thread of the insert.
(b)
Turn the tool counterclockwise to
the remove the insert.
Figure 51
Removing Tool P/N 64595
