How to Install Helicoil in an Aluminum Head

by C.L. Rease

Aluminum heads require strong threaded connections to keep an engine functioning correctly. The soft nature of aluminum allows threads to pull from their base material when under the strain and pressure of an operating engine. When threads strip from connecting points of an aluminum head, new -- stronger -- threads need to be installed to ensure the heads remain securely attached to the engine block. An installed HeliCoil threaded insert provides a secure threaded connecting point for accessories on engines with aluminum heads.

Step 1

Clean the area where the aluminum threads stripped from the hole in the head with a clean dry rag.

Step 2

Fill all holes around the hole with the damaged threads with paper towels to keep aluminum shavings from entering the ports of the head.

Step 3

Install the drill bit contained in a HeliCoil repair kit in the chuck of a drill motor. Coat the drill bit with cutting fluid. Drill the damaged hole to the correct size with the drill bit. Remove aluminum shavings from the hole with the tip of a clean rag.

Step 4

Secure the tap -- included with the repair kit -- in a tee-handle tap wrench. Coat the threads of the tap with cutting fluid and tap the drilled hole in the aluminum head. Clean aluminum shavings from the tapped hole with a clean rag.

Step 5

Thread a HeliCoil threaded insert on the end of the mandrel tool included with the repair kit. Coat the exterior threads of the insert with red threadlocking sealant. Set the end of the threaded insert in the tapped hole. Turn the handle of the mandrel clockwise to thread it in the hole. Continue turning the tool until the top of the insert wits flush with the surface of the head. Reverse your turning direction to remove the mandrel from the insert.

Step 6

Slide the end of the included tang break-off tool inside the installed threaded insert. Strike the back of the tool with a hammer to break the tang from the insert.

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