Main Cap Bolt Hole Thread Repair Procedure

The cylinder head bolt thread repair kit consists of the following items: See Figure .

• Drill (1).
• Tap (2).
• Installer (3).
• Alignment Pin (4).
• Bushing (5).
• Bolts (6).
• Fixture Plate (7).

1. Install fixture plate, bolt, and bushing, onto engine block.
2. Position alignment pin in desired hole and tighten fixture retaining bolts. See Figure .
   NOTE: Drill until stop collar of drill bit contacts the bushing.
3. Drill out damaged hole. See Figure .
4. Using compressed air, clean out any chips.
   • M6 inserts require a minimum drill depth of 15 mm (0.59 in).
   • M8 inserts require a minimum drill depth of 20 mm (0.79 in).
   • M10 inserts require a minimum drill depth of 23.5 mm (0.93 in).
   NOTE: Tap the new threads to proper depth by turning tap into hole until mark on tap aligns with top of bushing. See Figure .
5. Using a tap wrench, tap threads of drilled hole.
   • M6 inserts require a minimum tap depth of 15 mm (0.59 in).
   • M8 inserts require a minimum tap depth of 20 mm (0.79 in).
   • M10 inserts require a minimum tap depth of 23.5 mm (0.93 in).
6. Using compressed air, clean out any chips.
7. Spray cleaner GM P/N 12346139, or equivalent into hole.
8. Using compressed air, clean any cutting oil and chips out of hole.
   CAUTION: Do not allow oil or other foreign material to contact Outside Diameter (OD) of insert.
9. Lubricate threads of installer tool with driver oil. See Figure .
10. Install insert onto driver tool. See Figure .
11. Apply threadlock Loctite 277(tm), J42385-109, or equivalent to insert OD threads. See Figure .
    NOTE: Installer tool will tighten up before screwing completely through insert. This is acceptable. You are forming bottom threads of insert and mechanically locking insert to base material threads.
12. Install insert and driver into hole.
13. Rotate driver tool until mark on tool aligns with deck surface of engine block. See Figure .