Thread Repair - GMC T Series 1994 Repair Manual

t j | Measure (Figure 29)
• Gaging plastic at its widest point, using the scale
on the gaging plastic envelope (figure 29).
• If the clearance exceeds specifications, select a
new, correct size, connecting rod bearing and
remeasure the clearance.
• A standard or undersize bearing may produce the
proper clearance. Refer to the proper section for
bearing availability.
• Do not attempt to use shims or file the bearing to
obtain the needed clearance.
• If the clearance cannot be brought within specifica­
tions, recondition or replace the crankshaft. Do not
recondition a rolled fillet crankshaft.
+-► Remove or Disconnect
Gaging plastic.
Damaged threads may be reconditioned by drilling
out, rethreading, and installing a suitable thread insert.
Tools Required:
General purpose thread repair kits are available
commercially.
CAUTION: W ear safety glasses to avoid eye
damage.
1. Determ ine size, pitch, and depth of damaged
thread. If necessary, adjust stop collars on cutting
tool and tap to required depth.
Important
• Refer to the kit m anufacturer's instructions
regarding the size of drill and tap to be used.
2. Drill out damaged thread. Clean out chips.
DRILL HOLE TO
PROPER SIZE

THREAD REPAIR

B
TAP HOLE TO
PROPER SIZE
A. Measure Widest Point of Gaging
Plastic with Graduated Scale
Figure 29— Measuring the Gaging Plastic
3. Tap hole. Lubricate tap with light engine oil.
the thread.
Important
• Avoid build-up of chips. Back out the tap every
few turns and remove chips.
4. Thread the thread insert onto the mandrel of the
installer (figure 30). Engage the tang of the insert
onto the end of the mandrel.
5. Lubricate the insert with light engine oil (except
when installing in aluminum) and install.
Important
• When correctly installed, the insert should be
flush to one turn below the surface.
6. If the tang of the insert does not break off when
backing out the installer, break the tang off with a
drift.
INSTALL INSERT INTO
INSTALL INSERT
NEWLY THREADED
ON MANDREL
B4997
C le a n