Spark plugs that haven’t been changed for a long time can become one with the cylinder head. Fortunately, it’s possible to repair damaged threads instead of scrapping the head. There are a number of ways to repair stripped threads, you can insert a Helicoil. There are several types of repair inserts, but we prefer Helicoils.
A proper thread repair should last as long as the life of the car. This type of repair can be used for almost any threaded fastener, by the way. And that includes cast-iron, steel and aluminum parts.
Warning: Installing a Helicoil or other threaded insert looks simple — but it’s not. Any readers out there who wish to attempt it might want to practice a couple of times on scrap parts.