View source for Spark Plug Guide

Research by amceaglenest member "Jurjen"

The Eagle runs best on simple plugs.
Only disadvantage is that they wear out quickly (6000 mls) in combination with the high voltage ignition.
I don't like plugs with multiple ground electrodes, because they cannot be adjusted.
And last but not least, I like the ones that protrude into the combustion chamber better because I expect the flame front to be more even (less knocking and better MPG).
Engines that are burning oil, are better off with plugs that have less protrusion
See and read under tip protrusion:

http://en.wikipedia.org/wiki/Spark_plug

Here we go:

Truckplugs Champion 4412
Some off roaders like the truckplugs best, but they are not being made any more.

Normal plugs
Champion RC12ECC
Autolite 985
NGK ZFR5N
Denso QJ16HR-Q
Bosch FR9HC+

Premium plugs
Champion RC12PEC5
Autolite AP 985
Bosch FR9HP+

Don't use (or only in engines that burn oil, to prevent fouling up)
Champion RFN14LY (this is the plug advised by AMC)
NGK ZFR4-11
NGK ZFR5-11
NGK FR5-1

General data
Thread 14mm
Reach 3/4" (19mm)
Hex 5/8" (16mm)
extended projected tip