Cylinder Head Bolt Hole Thread Repair

Special Tools

• EN 42385-700  High Feature Thread Repair Kit
• EN 42385-2000  Thread Insert Kit

For equivalent regional tools, refer to Special Tools .

Fig 1: Cylinder Head Bolt Hole Thread Repair Kit Components

Courtesy of GENERAL MOTORS COMPANY

The cylinder head bolt hole thread repair tooling are in the kits EN 42385-2000  insert kit and EN 42385-700  kit. The cylinder head bolt hole thread repair components consist of the following:

• EN 42385-723 Drill (1)
• EN 42385-724 Tap (2)
• EN 42385-725 Installation driver (3)
• EN 42385-303 Alignment pin (4)
• EN 42385-302 Bushing (5)
• EN 42385-733 Bolts (6)
• EN 42385-401 Fixture plate (7)

When installed to the proper depth, the flange of the insert will be seated against the counterbore of the drilled/tapped hole.

Fig 2: Fixture Plate & Components - Cylinder Head Bolt Hole
Courtesy of GENERAL MOTORS COMPANY
1. Position the fixture plate (3) with the bushing (1) installed over the cylinder head bolt hole to be repaired (4).
2. Loosely install the fixture plate bolts (2) into the remaining cylinder head bolt holes.
Fig 3: Alignment Pin
Courtesy of GENERAL MOTORS COMPANY
3. Position the alignment pin (1) through the bushing and into the cylinder head bolt hole.
4. With the alignment pin in the desired cylinder head bolt hole, tighten the fixture retaining bolts (2).
5. Remove the alignment pin (1) from the cylinder head bolt hole.
Fig 4: Drilling Out Threads Of Damaged Hole - Cylinder Head Bolt Hole
Courtesy of GENERAL MOTORS COMPANY
NOTE:
• During the drilling process, it is necessary to repeatedly remove the drill and clean chips from the hole and the flutes of the drill.
• Drill the hole until the stop collar contacts the top of the drill bushing.
6. Drill out the threads of the damaged hole.
Fig 5: Cleaning Out Metal Chips
Courtesy of GENERAL MOTORS COMPANY
NOTE:

All chips must be removed from the drilled hole prior to tapping.

7. Using compressed air, clean out any chips.
Fig 6: Tapping Threads Of Drilled Hole Using Tapping Wrench - Cylinder Head Bolt Hole
Courtesy of GENERAL MOTORS COMPANY
NOTE:
• During the tapping process, it is necessary to repeatedly remove the tap and clean chips from the hole and the flutes of the tap.
• Ensure the tap has created full threads at least to the depth equal to the insert length.
8. Using a suitable tapping wrench, tap the threads of the drilled hole by hand only.
Fig 7: Fixture Plate, Drill Bushing & Tool Marking
Courtesy of GENERAL MOTORS COMPANY
9. In order to tap the new threads for the insert to the proper depth, rotate the tap into the cylinder head bolt hole until the mark (3) on the tap aligns with the top of the drill bushing (2).
Fig 8: Fixture Plate & Components - Cylinder Head Bolt Hole
Courtesy of GENERAL MOTORS COMPANY
NOTE:

Remove the fixture plate prior to installing the insert with the installer tool.

10. Remove the fixture plate bolts (2).
11. Remove the fixture plate (3) and bushing (1).
Fig 9: Cleaning Out Metal Chips
Courtesy of GENERAL MOTORS COMPANY
NOTE:

All chips must be removed from the tapped hole prior to insert installation.

12. Using compressed air, clean out any chips.
Fig 10: Spraying Cleaner Into Tapped Hole
Courtesy of GENERAL MOTORS COMPANY
13. Spray cleaner into the tapped hole. Refer to Adhesives, Fluids, Lubricants, and Sealers for recommended cleaner.
Fig 11: Cleaning Out Metal Chips
Courtesy of GENERAL MOTORS COMPANY
NOTE:

All chips must be removed from the tapped hole prior to insert installation.

14. Using compressed air, clean out any chips.
Fig 12: Lubricating Installer Tool Using Driver Oil
Courtesy of GENERAL MOTORS COMPANY
NOTE:

Do not allow oil or other foreign material to contact the outside diameter (OD) of the insert.

15. Lubricate the threads of the driver installation tool (2) with the EN 42385-110 (1).
Fig 13: Bushing Type Insert
Courtesy of GENERAL MOTORS COMPANY
16. Install the insert (2) onto the driver installation tool (1).
Fig 14: Applying Threadlock To Insert
Courtesy of GENERAL MOTORS COMPANY
17. Apply threadlock sealant, EN 42385-109, LOCTITE 277®; or equivalent (1) to the insert OD threads (2). Refer to Adhesives, Fluids, Lubricants, and Sealers for recommended sealant.
Fig 15: Installing Installation Driver By Hand
Courtesy of GENERAL MOTORS COMPANY
18. Install the insert and installation driver (1) into the tapped hole by hand only.
19. Start the insert into the threaded hole.
NOTE:

If the insert will not thread down until the flange contacts the counterbored surface remove the insert immediately with a screw extracting tool and inspect the tapped hole for any remaining chips and/or improper tapping.

20. Install the insert until the flange of the insert contacts the counterbored surface.
NOTE:

The driver installation tool will tighten up before screwing completely through the insert. This is acceptable. The threads at the bottom of the insert are being formed and the insert is mechanically locking the insert into the base material threads.

21. Continue to rotate the driver installation tool through the insert.
Fig 16: Driver Installation Tool & Surface Of Engine Block Deck
Courtesy of GENERAL MOTORS COMPANY
22. In order to completely form the new threads in the insert, rotate the driver installation tool through the insert until the mark (1) on the driver installation tool aligns with the surface of the engine block deck (2).
23. Inspect the insert for proper installation into the tapped hole.