Spark Plugs for 73 Dart Custom

Couple of comments.
- Copper is used in the centre electrode in a spark plug because of it's better heat conduction characteristics, not because it conducts electricity better.
- NGK was ridiculed by companies like Champion when NGK introduced the copper electrode. Now they all use it...including Champion.
- Iridium plugs can be a benefit in a performance engine, but in an oil burner. I would try NGK plugs with a '5' heat range.