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.

Once the insert is installed properly and to the proper depth, the spark plug can be installed. The company advises the use of only a “full-threaded” spark plug, and torquing it to 25 lbs.-ft. For ...

Kyle Smith The spark plug threads weren’t damaged so we figured the cylinder head wouldn’t be much worse. Kyle Smith When—not if—some damaged threads appear on your project, there is a lot going ...