Spark Plug Index Tool

Spark Plug Index Tool

The indexing of spark plugs involves choosing a set which enables the ground strap of the plug to point away from the piston dome. Oftentimes this is done when a large piston dome is used to maximize compression ratio. When this happens, the ground strap can come into contact with the dome causing the plug gap to close which will cause a misfiring spark plug. At one time, it was also thought to have the plug ground strap not interfere with the spark as it originated at the source. This however has proven to be a moot point and the only reason for assuring the ground strap is pointed away from the dome is for interference issues.

Today's engine builders and piston manufacturers do take note of the area where the plug might contact the dome and will usually assure there is enough clearance. However, when you're looking to build as much compression ratio as possible, losing even a little bit of dome will affect that. Even when there is enough clearance, it's still a wise move to index your plugs anyway as a matter of taking all precautions.

The job of indexing a set of plugs for your engine requires you to purchase at least ten plugs for an eight-cylinder engine, marking the location of the ground strap on the porcelain of the plug and screwing each one in and out of your cylinder heads noting the position. It's generally thought as long as the position falls within the 10:00 and 2:00 points, you will have enough clearance. The problem arises with having to do this every time you install a new set of plugs, bending over the side of an engine each time. The DRC Race Products Spark Plug Index Tool alleviates that issue.

Once you have a set which fits your cylinder heads, you simply install each plug into the Index Tool, marking the ground strap's position on the bottom of the Tool. The next time it calls for a new set of spark plugs, you can simply sit on your work bench, couch, etc., screwing plugs in and out of the Tool until you have a set which fits. The Tool will also safely store a complete set of spare spark plugs.

The Tool is manufactured from billet aluminum, black anodized and marked as far as the left and right side of the engine.

For more information call us at 570-658-3515.