cliffyk

On any particular vehicle--or am I supposed to guess?

On a 1970 Mustang, assuming a stock motor with a distributor, it doesn't matter--you probably should not run precious metal plugs at all--in 1970 they weren't even a wet dream shared by spark plug engineers...

stangcoupe1970

Maybe I should change my sig to avoid confusion or post in the 4.6 section

I have a 98 gt

cliffyk

OK, then what would happen is that 1/2 of your plugs would wear prematurely, with the side electrodes eroded. I do not know the exact polarity relationships of the EDIS, but it would be all plugs on either the left or right side of these relationships:

#1 / #6
#3 / #5
#4 / #7
#2 / #8

This is a good pictorial diagram of the EDIS:



FWIW: '96 to '98 4.6L engines use the EEC-IV system and the EDIS wasted spark ignition system; '99 to '04 use the EEC-V system and COPs.

stangcoupe1970

specs on the plugs i just put in:


NGK - Spark Plug
Part Number: 3403
Line: NGK

* G-Power
* TR55GP
* SOHC
* Per Car Quantity = 8
* Gap @ .054
* UPC: 87295134030

cliffyk

Those are double platinum plugs, you're all set...

The "double" part means that the center electrode has a platinum tip, and the side electrode has a platinum insert.

b96gtman

cliffy, i have a fully built stroker 96gt, cams and all,sitting at stock comression.i have never ran double plat plugs in my car. in fact i run autolite 103's. due to the fact they are 1 step cooler and a copper plug. A little better for performance. I always wondered why the Motor craft plugs all have the diff part numbers? Crazy info bro. But i have never had plugs wear out differently at all. I have msd coil packs on my car at the moment to. But if what u say is true(and i know it is) why would all the performance shops ive talked to and my tuner who is very reputable tell me to run copper plugs and not the PP plugs?

Brian

cliffyk

Because old ways die hard--for a very long time the world was considered flat by all "respected" scholars and anyone that said differently was a nut case...

Most likely you have not run the plugs for sufficient number of miles for the erosion to be apparent--this would take 25k+ miles to develop. Ford used the staggered (tip and side) platinum plugs because of the specified 100k service life.

As to the "copper" part that's a mostly marketing department thing--"copper" sounds good because we all know that copper is a good conductor of both heat and electricity.

The heat conduction part is irrelevant as spark plugs of a given heat range specification are designed to dissipate heat at the rate defined by that spec. Assuming that goal is met it, doesn't matter if the plug's core is made of copper, brass, aluminum, steel, or even petrified brontosaurus turd--all that matters is does the plug dissipate heat as per the specification.

The charming electrical characteristics of copper make good marketing speak too--however in reality the copper is a core plug inserted into the nickel-chrome alloy center electrode and due to a phenomenon known a "skin-effect" has nothing to do with conducting the electricity that creates the spark. It also costs a bit less than nickel-chrome alloy so between the marketing and cost benefits it's win-win...

Beyond that, why would having 1-1/2 inches of copper conductor, connected to the coil with a wire that has 3kΩ to 15kΩ per foot resistance (or at the end of a stainless steel "spring" as in the COP system), make a rat's back-end worth of difference in spark energy?

swarthyfellow

I have learned so much today... I have always wondered way the plug wires cross over when there are 2 packs on each side. Thanks.