The top engine builders all know that to wring every ounce of power out of an engine, little things like positioning the spark plug electrode become important. This is also critical in an engine with domed pistons because the piston can close the plug gap if not positioned properly. Because you set up our Spark Plug Indexer to match your cylinder heads, you can position your plugs in the tool exactly how you will want them in any particular cylinder. The moveable bushings in our indexer plate allow you to set it up for any set of cylinder heads. You can fit plugs to a particular cylinder or use index washers to tweak the plugs into position. This tool really speeds up the plug indexing process.