Go to : http://www.richer-engineering.com/Series/spark_plugs.php for more lengthy explanation
In a nut shell:
For the land Rover 2.25, the required spark plug is:
14 MM plug thread
3/4″ reach (length of the threaded portion of the plug)
Gasketed seat
13/16″ hex
Resistor (optional – see above)
Copper core
Medium heat range (range from hot to cold)
In looking at this I hear you ask, “What about platinum plugs? Iridium? Multiple electrode?”
In short, don’t bother. Not worth the effort for an engine as lightly stressed as the old 2.25. Personally, I don’t even like them in my Rover V8s. If the engine isn’t designed to use them it’s not worth the effort.
For the Rover 2.25:
Champion RN11YC4
AC Delco R44XL
Autolite 64
NGK BPR5ES
NipponDenso W16EPR-U
Bosch WR8DS
Me: I am using Bosch platinum+4, works ok…. One more thing, while you are at it… checking the condition of spark pug may be a good indication how healthy is your engine and electrical system in general
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