An inexpensive method for repairing a damaged spark plug hole of a cylinder engine includes drilling the damaged spark plug hole using a drill bit, tapping the drilled spark plug hole, threading a steel insert into the threaded hole and making a spark plug seat. The depth of the drilling, tapping and threading is limited by a stopper. A set of new tools are used to realize the foregoing process. All these procedures can be done while the cylinder having the damaged spark plug hole on the vehicle. The resulting hole is stronger and more durable than the original spark plug hole in the aluminum cylinder head.