Does anyone have numbers to back up that copper plugs will produce more hp than platinum plugs or is it negligible? Specifically anyone with a heads/cam car.

 

The purpose of the using Cu plugs isn't to make more power - it's to reduce hot-spotting, and so reduce the chances of pre-ignition/detonation. The only way you will make more power is if your old plugs were bad or you were already getting into the pre-ignition zone slightly. The "higher-performance" your engine is, the more important it is to run copper plugs.

On the other hand if longevity is your concern, then Iridium plugs are a better choice that Platinum. The Ir plugs should last longer and allow a larger gap than Pt plugs. The also are less prone to hot-spotting than Pt plugs if you get similarly sized center electrodes. NGK and Denso are the 2 Ir plugs I am aware of.

 

Copper conducts electricity better than platinum but "wears out" faster.
Platinum wears longer but conducts less electricity.
Copper possibly has a "hotter" spark so better combustion.
Platinum allows the "100,000" tune-up label.
I'll take doing the job better to doing the job longer, thank you very much!
Hope this helps.
:chevy

 

Silversport couldn't have said it better...
i love my copper plugs :eek:

 

Copper for performance
Plats for lazy people
How's the hood coming?

 

Actually though the electrodes on copper plugs are normally some sort of Steel-Ni alloy, so the electrical properties of copper aren't the only issue (if the electrodes were copper you would be lucky to get 500 miles out of the plugs.

Also electrical conduction in the spark plugs isn't primarily based on resistance of the metals. The resistance of the air gap is MANY orders of magnitude greater than the plug resistance, and compared to it the small deltas in plug Resistance are irrelevant.

Now sharp edges and small electrodes allow the spark to jump "easier" across the gap (increasing the point charge in a way) - and since Pt is a much harder/more durable metal than Steel/Ni (copper plugs), the electrode can be made smaller/more jagged.

Platinum plugs actually require LESS voltage to fire than Cu plugs - hence the resistance of the plug doesn't really matter. Now this also means a Pt plug at the same gap will have a weaker spark because of the way the coil works, which is why you need to open up the gap on Pt plugs.

But the same small/jagged electrode that makes sparking easier is horrible for anti-hotspotting measures, and does even more to accentuate the bad thermal conduction of Pt.

Ir is easier to fire or the same as Pt (depending on the electrode design and gap), and has better thermal conduction as well as better wear.


That said I of course still use Cu since performance/no-detonation is my primary concern, but if longevity is then you should use Ir. There is really no good reason to use Pt ever anymore.