Specification Sheet
NGK Spark Plug Specication Chart
48
Spark plug charts are sorted by thread size, thread reach, hex size. Hotter plugs are listed above the colder plugs. Plug images are located on
the opposite page.
NGK Racing NGK Standard
Part
No.
Stock
No.
Image
Part
No.
Stock
No.
Image
Racing Spark Plugs
14mm Spark Plugs cont’d
3/4” Reach
13/16” Hex R6712-9 5644 186 AC
Surface Discharge R6712-10 5421 186 AC
Gasket, Loose
Resistor
3/4” Reach
13/16” Hex R5649-9 4711 186 AC
Surface Discharge R5649-10 6498 186 AC
Gasket, Loose R5649-11 4168 186 AC
Non-Resistor
21mm Reach R7440A-9L 3795 102 CC
13/16” Hex R7420-9 6448 332 JL
Iridium R7440A-10L 4282 102 CC
Low Angle Ground
Electrode
R7420-10 5501
Gasket, Solid R7420-105 4857 332 JL
Resistor R7420-11 7756 332 JL
21.5mm Reach
13/16” Hex R6725-10 3342 79 BG
Platinum R6725-105 3857 79 BG
Low Angle Ground
Electrode
R6725-11 4311 79 BG
Gasket, Solid R6725-115 4482 79 BG
Resistor
22mm Reach
5/8” Hex R7282A-10 3920 21 IC
Iridium R7282A-105 4614 21 IC
Low Angle
Ground Electrode
R7282A-11 4754 21 IC
Short
Gasket, Solid
Resistor
26.5mm Reach
5/8” Hex R7437-8 4901 144 DI
Iridium R7437-9 4654 144 DI
Projected R7437-10 4655 144 DI
Gasket, Solid
Resistor
26.5mm Reach
5/8” Hex R7438-8 4905 145 DJ
Iridium R7438-9 4656 145 DJ
Low Angle
Ground Electrode
R7438-10 4657 145 DJ
Gasket, Solid
Resistor
Due to the extreme modications in racing applications, these spark plugs are not warranted
NGK Racing NGK Standard
Part
No.
Stock
No.
Image
Part
No.
Stock
No.
Image
Racing Spark Plugs
18mm Spark Plugs
16mm Reach
25.4mm Hex R8102A-10 6813 261 HH
Gasket, Loose
Non-Resistor
NGK Spark Plug Prole & Tip Images