Carmakers continually look for more ways to increase efficiency, improve airflow and boost performance. Unfortunately, increased power usually comes at ever increasing costs, and with the days of screw-tuned carburetors long behind us, it has become harder to find a cheap power producer. Enter spark plug indexing. This simple technique has been in use throughout decades of motor racing because of its ability to improve power output by 1-2 percent.
Indexing your spark plugs is based around a simple concept: the closer the spark is to the ignition source, the more efficiently each of the cylinders inside your engine will produce power. The ideal position for the open face of each spark plug is to point toward the fuel/air intake value where ignition will not be impeded.
Now here is the bit where your pre-school art class comes into play. Knowing the direction the spark plug’s electrode will face once screwed tightly into the engine block is a bit difficult without the use of your X-ray glasses. Instead, you’ll need to mark, or “index,” the position of the spark plug’s electrode on the upper most porcelain section with a permanent marker. When reinserting the spark plugs, screw them in so the marked part faces toward the fuel/air valve. You’ve just successfully made your engine more efficient.