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. (Photograph by Chris ...

The gap between the center and side electrodes needs to be an exact distance across; otherwise, your plugs won't fire efficiently. Remember: Gap new as well as old spark plugs, even if the package ...

All spark plugs may look the same to the untrained eye. Unfortunately, nothing could be further from the truth. For starters, spark plugs come in many types that are mainly differentiated by the ...