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I'm curious to hear what folks think about this as well. Obviously, you would want to change all 16 plugs. I don't see any need in changing the coil pack unit unless you have a misfire issue or some reason to suspect one may be bad. I'm not sure about the wires though.
 

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I am about to do them again, I usually like to change out all the plugs. I have heard that you can change just the main plugs and those I believe are the ones under the spark plug wire. I installed Iridium plugs last time and they perfoirmed great. But I am going to put in the NGK5306 v groove this time. I didn't want to spend $200.00 for plugs again.
 

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I believe the 16 plugs don't all get changed at once

The main 8 plugs have to be changed every time,
i believe the upper set could be changed every other time or even longer

the upper set don't really see much firing

I don't understand this crazy setup, it is almost like the upper set just makes sure of a cleaner burn. a smog thing
 

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There is some good info about the hemi engine here and a specific section on the dual plug setup.

http://www.allpar.com/mopar/new-mopar-hemi.html

Unless I am misunderstanding it appears to me that each plug on a given cylinder fires on time per cycle...they just fire at different times. If this is the case, I would think the plugs would have the same life expectancy and recommended replacement time.

I know the newer 4.7s that have two plugs per cylinder have two different plugs and change intervals from the factory. The easier ones to change are standard copper and should be changed at 30K miles and the harder ones are iridium and are good for 100K miles. I don't think the third gen hemis are like that though because all of the plugs are located side by side (in eight pairs) and relatively easy to get to.

Also, directly from my 2004 hemi owner's manual....

* Replace spark plugs at 30K miles (it doesn't specify certain plugs....just says replace spark plugs)

* Replace spark plugs and ignition wires at 60K miles

Hope that helps.
 
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