13-05-2025, 07:16 PM
Hi
I don't know if it's relevant, but here are some of NGK's recommendations for spark plug torque:
18 mm Flat seat in Cast Iron 25.3 to 32.5 lbs-ft
18 mm Flat seat in Aluminium 25.3 to 32.5 lbs-ft
14 mm Flat seat in Cast Iron 18 to 25.3 lbs-ft
14 mm Flat seat in Aluminium 18 to 21.6 lbs-ft
This ought to give a gas-tight seal, so any bubbling suggests a problem. I have sometimes found the seating areas in the head a little bumpy, but you say these have been spot faced.
I don't know if it's relevant, but here are some of NGK's recommendations for spark plug torque:
18 mm Flat seat in Cast Iron 25.3 to 32.5 lbs-ft
18 mm Flat seat in Aluminium 25.3 to 32.5 lbs-ft
14 mm Flat seat in Cast Iron 18 to 25.3 lbs-ft
14 mm Flat seat in Aluminium 18 to 21.6 lbs-ft
This ought to give a gas-tight seal, so any bubbling suggests a problem. I have sometimes found the seating areas in the head a little bumpy, but you say these have been spot faced.