Heli-coil 5523-12 Spark Plug Thread Repair Kit M12 X 1.25

Product Description

The HELI-COIL 5523-12 is a spark plug thread repair kit designed to restore damaged or stripped M12 x 1.25 metric fine threads in cylinder heads. The kit provides a complete repair solution in a single package, including a drill, tap, installation tool, and tang removal tool, along with 24 wire thread inserts. Licensed mechanics, engine technicians, and fleet maintenance shops use this kit to bring stripped spark plug holes back to factory-spec thread engagement without replacing the cylinder head. The inserts lock into the repaired bore and provide a durable threaded surface for standard M12 x 1.25 spark plug installations.

This kit is suited for automotive, powersports, and small-engine applications where M12 x 1.25 spark plug threads are present. It is commonly used in shop environments during engine rebuilds, post-overheating repairs, or any situation where a spark plug has seized and pulled threads on removal. The included tooling covers the full repair sequence from drilling out the damaged thread to final insert installation, making it a self-contained solution for field and shop use.

Key Features

• Repairs M12 x 1.25 metric fine spark plug threads in cylinder heads
• Includes drill, tap, installation tool, and tang removal tool for a complete repair sequence
• 24 wire thread inserts included, supporting multiple repairs per kit
• Insert packages R482-1 and R482-2 included for insert replenishment
• Installation tool part number 4971-12 and tap part number 1030-12 for easy replacement sourcing
• Metric fine thread standard ensures compatibility with OEM spark plug specifications

Compatibility

Designed for use in any engine application with M12 x 1.25 metric fine spark plug thread bores requiring thread repair or restoration.

Installation Notes

Thread repair work on cylinder heads should be performed by a qualified engine technician or machinist. Disable the ignition system and remove all spark plugs before beginning the repair sequence. Follow the drill, tap, and insert installation steps in order using only the included tooling to maintain proper thread alignment and insert seating. Do not exceed the drill depth specified for the insert length to avoid breakthrough into the combustion chamber.