Repair Damaged or Worn Threads

Damaged or worn threads (including aluminum head spark plug threads) can be repaired. Essentially, this repair consists of:
1. Drilling out worn or damaged threads.
2. Tapping the hole with a special Heli-Coil Tap, or equivalent.
3. Installing an insert into the tapped hole to bring the hole back to its original thread size.

CAUTION: Be sure that the tapped holes maintain the original centerline.

Heli-Coil tools and inserts are readily available from automotive parts jobbers.