Section VI. PISTONS, PINS, AND RINGS

TM 10-3930-633-34

(3) It is imperative to pull the plug into the

(4) Oversize (OS) plugs are identified by the

machined bore by using a properly designed tool.

OS stamped in the flat located on the cup side of

Under no circumstances is the plug to be driven

the plug.

into the bore using a tool that contacts the flange.

b. Installation (Cup Type).

This method will damage the sealing edge and will

(1) Coat the plug and bore lightly with an oil

result in leakage and/or plug blow out.

resistant or water resistant sealer and install as

(4) The flanged (tailing) edge must be below

follows :

the chamfered edge of the bore to effectively seal

(2) Cup type core plugs (fig. 6-24) are in-

the plugged bore.

stalled with the flanged edge outward. The

maximum diameter of this plug is located at the

(5) If the core plug replacing tool has a depth

seating surface, do not seat the tool against a

outer edge of the flange. The flange on cup type

non-machined (casting) surface.

plugs flares outward with the largest diameter at

c. Installation ( Expansion Type ).

the outer (sealing) edge.

(1) Expansion type core plugs are installed

with the flanged edge inward. The maximum

diameter of this plug is located at the base of the

flange with the flange flaring inward.

(2) It is imperative to push or drive the plug

into the machined bore using a properly designed

tool, Under no circumstances is the plug to be

driven using a tool that contacts the crowned

portion of the plug. This method will expand the

plug prior to installation and may damage the

plug and/or plug bore.

(3) When installed the trailing (maximum)

diameter must be below the chamfered edge of the

bore to effectively seal the plugged bore.

(4) If the core plug replacing tool has a depth

seating surface, do not seat the tool against a cast

surface.

Figure 6-24. Core Plug Installation

Section VI. PISTONS, PINS, AND RINGS

caustic cleaning solution or a wire brush to clean

6-26. Cleaning and Inspection

pistons.

a. Cleaning.

(2) Clean the ring groove with a ring groove

(1) Remove deposits from the piston sur-

cleaner (see figure 6-25). Make sure the oil ring

faces. Clean gum or varnish from the piston skirt,

slots are clean.

piston pins and rings with solvent. Do not use a

6-23