NGK Iridium Spark Plug Gap

Do NGK Iridium plugs need to be gapped? The answer to this question is yes. For your engine to perform at optimum, the spark plugs in play should have the necessary spacing. It is thus vital that you get hold of the NGK spark plug gap size chart and adhere to the same. Why is this important? The spark plug needs this gap as it affects the firing temperature. This feature also affects the burning of fuel and air in the engine. And this will ultimately affect the performance of the car. The wider you open the gap, the more the sparks created, and this can increase the efficiency of the engine.

In some cases, you may find that this widening is in play, such as in customized engines. When gapping spark plugs, you must pay a great deal of attention to measurements and adjustments; else, you could get it wrong. Before getting into dimensions, let’s delve a little into NGK spark plugs.

Are NGK Spark Plugs pre-gapped? You probably have this and other questions running through your mind. Most of the information as to these plugs is available in the NGK spark plug gap chart PDF. There are five things you should know about these plugs. For one, they have trivalent plating. As such, they can resist corrosion owing to exposure to chemicals and moisture.

This coating also works as a release agent when removing the plugs. Note that these plugs get installed at the factory when dry, devoid of the use of anti-seize. People often over-tighten the plugs when using anti-seize, and you should thus avoid this. It also helps to note that the anti-seize compound can alter torque and lead to thread breakage.

Secondly, they feature a corona stain, which appears as discoloration. It owes to the accumulation of oil and dirt particles around the plug. It occurs due to static electricity released by the plugs. This tan is normal, and you should not have any concerns about it. Some people have mistaken it for broken seals inside the plugs.

What gap should my spark plugs be? This information is available in your car manual. Where you are in doubt, you should engage an expert on this matter. Otherwise, you could compromise the spark plug gap performance. Let’s get started on the measurements.


When getting new plugs, you must understand the gap that you should leave between the two electrodes. Car measurements differ, and you can thus not use anything that you find on the market. In most cases, the gaps should be in the regions of 0.028 to 0.06 inches. This information is available in your owner’s manual. Where you cannot get it, you can talk to an expert at the auto parts store.

When working with a modified engine, you will end up using smaller gap settings. It is the case to account for the power moving through the engine. Here is a quick tip. The more the power generated, the smaller the gap should be. You can use this rule of thumb when checking gap on iridium plugs.

You may have some queries as to how to gap spark plugs without tool. While this may be possible, you will get the best results when using the appropriate gap tool. Luckily, there is a wide selection of tools from which you can choose. As such, you do not have to limit yourself in this regard. Most tools will have a flat edge, which helps in bending the bottom electrode to help in the adjustment of the gap.

The cheapest tool is the coin-style gap. Here, you run the coin through the gap until you find where it stops. The edge has markings similar to those in a ruler and shows the thickness of the points. You can use this tool when checking the efficiency of the gaps, or widening the gaps as you run the coin.

A wire coin gap is similar to the coin style gap, only that it has varying measurements along its length. The other option is the blade-style feeler gauge, which is quite versatile. It has blades of different widths that you can use to measure as well as adjust the gaps.

NGK spark plugs should be clean when straight out of the box. However, if you wish to use a plug that has been in the car, you should clean it with a cloth. It might have some soot at the contact points, and this can interfere with the reading. If the dirt does not come off with ease, you can use quick-drying alcohol for this process. If this does not help, think of getting new plugs. You can now measure the gaps using the appropriate tool.


You may or may not need to adjust the gap. Where the tool passes through the gap and does not touch the electrodes where it should, the gap is too wide. Where the tool cannot fit between the electrodes, the gap needs some widening. If the fit is close to the measurement, you can proceed to install the plug.

Do gaps need Denso Iridium spark plugs? In most cases, you will find that you can use the plug without gapping it. It owes to the specs manufactured at present. However, when dealing with a modified engine, you should adjust the NGK iridium spark plugs as needed. In this way, you can tell if the 49cc spark plug gap will work for the plug you have in mind.

You can now use your tool to adjust the bottom electrode. It should be such that you hold the spark plug with the electrodes facing the floor. From here, you can bend the bottom outward or inward, based on the gap needs.

Ensure that you do not bend more than 0.02 fractions of an inch as the plug cannot take much pressure. If you damage the plug, misfires are likely to happen. Where you cannot bend the plug using the tool, you can make the adjustment on a flat surface to add to the pressure.

You can now measure the gap again and make adjustments where you deem it necessary. When doing so, you should not touch the center electrode as you could damage the core. If this happens, you will need to get another plug. It also helps to be gentle during this exercise; else, you will snap off the electrode. Use as little pressure as you can when bending, and you should be fine.

Note that some plugs come pre-gapped, and you can find this information on the inside flap of the box. In this case, you will not have much work to do. All the best!

Editorial Staff

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