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Technical Information

Q&A


PRACTICAL INFORMATION
Q18
Is there a specified tightening torque for the spark plug?
A
The tightening torque for a spark plug changes with the diameter of the spark plug.
The following are the recommended torque values.
illustratiton
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When installing the spark plug, first screw it in by hand. Once the gasket has made contact with the cylinder head, use the torque wrench to tighten it to the tightening torque shown below.
photo A rubber pipe as shown in the figure to the right is a good substitute for hand tightening/removing spark plugs.
 Tightening torque
Plug thread diameter Tightening torque
18 mm 35 to 40N·m (3.5 to 4.0 kgm)
14 mm 25 to 30N·m (2.5 to 3.0 kgm)
12 mm 15 to 20N·m (1.5 to 2.0 kgm)
10 mm 10 to 12N·m (1.0 to 1.2 kgm)
8 mm 8 to 10N·m (0.8 to 1.0 kgm)
 Tapered seat type For (spark plugs without gaskets)
Tightening torque
10 to 20 N·m (1.0 to 2.0 kg-m)
The tightening angle for both new and reused spark plugs is 1/16th of a turn.
For reference When it is difficult to use a torque wrench, or when you don't have a torque wrench, tighten the spark plug to the tightening angle shown in the illustration in accordance with the thread diameter of the spark plug.
Spark plugs with thread diameter of 18 and 14 mm
photo
Spark plugs with thread diameter of 12 and 10 mm
photo
Spark plugs with thread diameter of 8 mm
photo
Taper seat type
New plugs Reused
About 1/16 rotations
(22.5°)
About 1/16 rotations
(22.5°)
Copper gasket type
New plugs Reused
About 1/12 rotations
(30°)
About 1/24 rotations
(15°)
  [ attention ] Please note that the turning angle of a past plug and tightening is different about the following product number.
BCPR6ED BKR5EKUC BKR6EKE IZFR5C
BCPR6EKD BKR5EKUD BKR5ETUA PZFR5C
BCPR7EKD BKR6EKUC HB6AIX-11P R6469-9
BCPR7EDIX BKR6EKUD HB6BIX-11P R6918C-9
New Plugs About 1/3 rotations
Reused About 1/12 rotations
DILZKR7A11GS ILZKR7B11GS ILZKR7B-11S
SILKR8A-S R2556B-* R2558A-*
New Plugs About 1/4 rotations
Reused About 1/8 rotations
CPR6EA-9S CR8EH-9S CR9EH-9S IMR8C-9HES
IMR9C-9HES IMR9D-9H IMR9E-9HES SILMAR9A9S
SILMAR10A9S SILR6A7S SILR7A7S SPMR8A6HDG
R0409B-* R0451B-8    
New Plugs About 1/6 rotations
Reused About 1/12 rotations
The heat value enters for * of the end of R2556B-*, R2558A-*, and R0409B-*.
* There are some exceptions. Look at the adaptation for more information.
 Examples of common installation problems and advise to avoid them.
Thread damage from installation Metal shell damage Cracked insulator Examples of bad spark plug wrench usage
photo photo photo photo
Spark plug is inserted at an angle during installation Excessive tightening torque Spark plug wrench slipped or used at an angle
Do not use the wrench at first.
Start by installing the spark plug by hand.
Tighten to recommended torque. Use a hex-type wrench that is less likely to slip.
Copyright(c) 2006 NGK SPARK PLUG CO.,LTD. all rights reserved.