Installing Heli-Coil Inserts In Caterpillar Cylinder Heads{1117} Caterpillar

Installation of Heli-Coil thread inserts provides a relatively easy and inexpensive method of salvaging cylinder heads in which the threads for precombustion chambers or direct injection adapters have been damaged.

1. Remove the precombustion chamber or adapter seat gasket and clean the seat.

2. Insert drill guide (4) in the precombustion chamber or adapter opening of the head, with the end of the drill guide seated in the seat gasket counterbore.

3. Drill out the damaged threads, remove the drill guide, and clean all metal shavings from the opening.

4. Place tap guide (3) over the shank of tap (1) and install the tap guide in the cylinder head.

5. Tap the hole, remove the tap and guide, and thoroughly clean the threads.

6. Place the proper prewinder (5), for the size insert to be installed, into the counterbored section of sleeve assembly (6) with the hole in the prewinder aligned with the pin on the leaf spring. Be sure the smaller diameter of the prewinder is to the outside of the sleeve assembly. Lift the spring, position the prewinder at the bottom of the sleeve counterbore, and insert the spring pin into the prewinder hole.

7. Select the corresponding size nib (8) and attach to a .50" (12.7) square drive wrench. Place thread insert (7) on the nib so the tang engages the slot of the nib, with the tang end toward the mouth of the slot. Hold the drive wrench upright so the insert will stay on the nib, then slide the nib and insert into sleeve assembly (6) until the prewinder rests on the insert. Hold the sleeve assembly in one hand and revolve the drive wrench in a clockwise direction with slight forward pressure until the insert is wound into the prewinder three or four turns.

8. Place the tool in the tapped hole, and press sleeve assembly (6) downward firmly and flat against the work. Press the drive wrench downward slightly and revolve it clockwise until winding resistance disappears. If the insert binds, permit the sleeve assembly to revolve clockwise until the binding is relieved. Remove the inserting tool and check the insert for possible cross threading. Break off the tang. The precombustion chamber or adapter can now be installed.