combust-sbWhen you’re looking to get every last ounce of power out of an engine, you may happen upon some of the tips and tricks that professional racers and engine builders have been using for years to get ahead of the competition. One such instance allows you to garner some addition horsepower hidden in your engine’s ignition system. The topic that we’re eluding to involves one essential portion of the internal combustion engine, the spark plugs

While ensuring a plug has the proper gap and heat range is a priority, an area that gets overlooked is the indexing of these components. Investing the time to perform this small task will better the spark plugs ability to supply a complete fuel burn; which results in greater power output.


The mechanics behind indexing a set of plugs are quite simple. Verifying that the electrode gap of the spark plug is facing the air/fuel mixture allows the mixture to ignite more efficiently. Indexing plugs can only be achieved when a conventional-type “gapped” plug is the threaded into the head. Merely throwing in a set of plugs, without aligning the gap can cause the grounding strap to shield the electrode. This, in turn, will require the air/fuel mixture to travel farther to be properly ignited by the plug, this kind of impedance can affect timing and result in an incomplete burn.


The grounding strap of this plug is shielding the electrode, and will result in a less effective burn.

While it can be time-consuming, this simple practice only requires a few items that, chances are, you have laying around the garage. After gathering up some standard tools, like a spark plug socket, ratchet, and a marker we can get started.

After creating a reference mark on a visible portion of the body, indicating the location of the gap side, the spark plug can be screwed into the head.

Second, simply install the plug into the head and discern the direction the reference mark points, ideally, you want the gap to face the intake valve if this engine features a standard fuel injected or carbureted setup. This may require multiple attempts with different plugs to achieve the end result. This critical step is the time-consuming portion of the process, and will possibly require more than a few boxes of plugs. Another way to solve this dilemma is to utilize a set of copper indexing washers, that will give you control more control over the plugs position thanks to their varying thicknesses.

Notice how the gap side of the plug is directed to the intake valve? This provides the desired fuel mixture combustion that yields a greater horsepower output.

Indexing plugs can be one of the cheapest horsepower modification that you can perform to your beloved vehicle. It is a practice that will ensure that your ignition system is delivering the most potent ignition it can produce, resulting in a maximum burn that permeates the entire combustion chamber. So, get yourself a marker and a box of plugs and make the most of what indexing can provide.