The best way to determine what temperature spark plug is needed is to consider the engine's compression ratio, overall horse power level, fuel type, and ignition system. Under most circumstances, the colder the plug is, the less protruded the center electrode will be from the shell. The short, thick insulator nose will withstand the heat better and transfer the heat to the shell faster. The long, thin insulator nose will heat up faster and will not transfer the heat to the shell as fast. The hotter plug will have a long, thin insulator nose, while a colder plug will have a short, thick insulator nose. The spark plugs insulator nose design is usually a great indication to the heat range of the spark plug. If the temperature of a spark plug exceeds 870☌ overheating may occur leading to spark plug and possible engine damage.' When too many carbon deposits accumulate along the insulator nose carbon fouling occurs and engine misfire may occur. At 450☌ the spark plug reaches its self cleaning temperature this means that carbon deposits which are produced during combustion are actively burnt off the insulator nose. PER NGK: 'The operating temperature of a spark plug varies between 450-870☌.

If the spark plug is too cold, it can cause plug fouling by allowing deposits to build up on the spark plug due to weak ignition spark. If the spark plug is too hot, it can cause pre-ignition, melting the spark plugs electrode and causing engine failure. Higher horse power engines produce higher combustion cylinder temperatures requiring a colder spark plug in order to resist the heat buildup and maintain optimal operating temperature. Lower horse power engines produce less combustion cylinder temperatures requiring a hotter spark plug in order to maintain optimal operating temperature. A hotter spark plug will heat up faster from the combustion temperatures, while a colder spark plug will provide more resistance to the combustion cylinder’s heat. The term hot or cold refers to the thermal characteristics of the spark plug. Determine the plug temperature you need.The copper core allows the plug to heat up quickly while also allowing it to dissipate the heat quickly. However, due to the fact it will melt at a lower cylinder temperature, it is a more forgiving in the event that the tune is off. The nickel-alloy plug does not last as long as a platinum or an iridium plug. The nickel-alloy body is made from a softer material. The non-projected plug will dissipate the heat that is absorbed from the combustion chamber to the head faster due to the shorter traveling distance. A non-projected spark plug has a shorter distance from the plug’s center electrode to the threaded shell, placing the ground electrode not as far into the combustion chamber. As a result, the projected spark plug has an increased distance that the heat has to travel through the insulator nose dissipating into the head. A projected spark plug has an increased distance from the plug’s center electrode to the plug’s threaded shell, placing the ground electrode further into the combustion chamber. Non-projected is a term that refers to how far the insulator nose of the spark plug protrudes out of the shell and into the combustion chamber. For nitrous applications, a non-projected spark plug with a nickel-alloy body and copper core is recommended.For many late-model EFI applications, Brisk may be the only thing available. It is an affordable plug and easy to read. I personally prefer to use NGK when possible. The three most common brands are NGK, Autolite, and Brisk. Determine the brand plug you will be using.Different heads require different reach plugs. You will also need to know the thread reach of the plug. Determine if your head requires a gasket seat or tapered seat spark plug.There are many different spark plug brands and styles. Spark plug choice plays a huge role in the information you will receive from looking at the spark plug during tuning.

Ngk heat range chart