When we say “spark plug size”, we usually mean the diameter of the threads of the spark plug. The two most common spark plug sizes in modern motorcycles and small cars are 14mm and 18mm. Some automobile manufacturers also use 16mm high-thread count spark plugs and 12mm long-reach spark plugs.
Spark plugs are available in two thread size options for motorcycles — 1/2 and 3/4 inches. For other vehicles, spark plug threads are also available in thread sizes like 8, 10, 12, 14, and 18 mm.
The most common spark plug socket sizes are the 5/8 inch and 13/16 inch sockets.
While you should buy spark plugs in matching sets for your vehicle, not all spark plugs are universal. Spark plugs come in different sizes with different gaps and are manufactured using a variety of metals. Finding the ones that you need can be difficult.
The diameter can be measured using a set of Calipers. The pitch can be measured using a Thread Gauge.
16mm = 5/8 inch. 17mm = almost 11/16 inch. 18mm = just over 11/16 inch. 19mm = 3/4 inch.
NGK Spark Plug: Marine, Nickel Core, 5/8 in Hex Size, 0.551 in Thread Size, 0.46 in Thread Reach.
Spark Plug Sockets
Though you can technically use any socket of the right size, we recommend using the kind specifically made to pair with spark plugs. These special sockets contain rubber isolators inside intended to absorb any possible vibration within and protect the glass featured along the spark plug.
Nowadays there are different kinds of spark plugs available in the markets to choose from i.e. copper, platinum and Iridium spark plugs. The copper spark plug is the most commonly used spark plug as it is the cheapest among the three.
If you're a tuner or engine builder in search of the perfect spark plug for your current project, pay special attention to the hex size required. Remember to take into consideration not only the diameter of the cylinder head, but also the added thickness of the plug socket needed for installation.
Tighten the spark plug finger-tight until the gasket reaches the cylinder head, then tighten about ½ – ⅔ turn more with a spark plug wrench.
The copper spark plug is the most common and cheapest plug available. While almost all spark plugs feature a copper core, many people refer to the common spark plug as a “copper” spark plug. A standard spark plug typically features a nickel-alloy outer material fused to the copper-core electrodes.
When we say “spark plug size”, we usually mean the diameter of the threads of the spark plug. The two most common spark plug sizes in modern motorcycles and small cars are 14mm and 18mm. Some automobile manufacturers also use 16mm high-thread count spark plugs and 12mm long-reach spark plugs.
A: M14 and 14mm are the same thing. M14 means that the kit is 14mm.
SPARK PLUG SPANNER SOCKET FOR 14mm SPARK PLUGS (21MM SOCKET) WITH T-BAR.
To remove spark plugs, you need a spark plug removal tool that grabs and twists the spark plugs inside your vehicle's engine. Because spark plugs can be in awkward positions, you may also need an extension for your spark plug socket.
All spark plug manufacturers cross-reference their plugs with other brands so their brand can be interchanged with other brands. For most applications, there are usually a variety of brands that are interchangeable.
Do Spark Plugs Always Have to Be Gapped? Not always. In the past, it was necessary to gap spark plugs, but today spark plugs are usually pre-gapped. It is advisable to double check that the gap is correctly set to the vehicle's recommended setting when installing spark plugs.
When a thread size is expressed in a set of two numbers, for example, 14x1. 25 or M14x1. 25 the first number is the thread diameter and the second number is the thread pitch. Search for spark plugs by specifications and dimensions.
Anti-seize
This silver or chrome-colored finish on the threads is designed to provide corrosion resistance against moisture and chemicals. The coating also acts as a release agent during spark plug removal.
Dielectric grease is commonly used to seal the connection between the spark plugs and the spark plug wire.
Do the math and 16mm comes to 0.005" over 5/8", so it seems that a snug-fit 16mm tool will work for a 5/8 plug, and a loose-fit 5/8" tool will work for a 16mm plug.