I went to good ol' rockauto for tune up parts and got the reliable champion copper plugs I've been using for years. When I received them I saw that they were a different size than the ones I currently had in the vehicle. New plug on the left, old one on the right. Would it be acceptable to run the longer plug?

 

If either of those are your old spark plugs then you don't need new ones.

 

totally different heat range, and might get smashed by piston?? looks longer

 

The longer one is a hotter plug, but they'll both work. If after a couple thousand miles you see carbon buildup around the plug, you can switch to the hotter plug. I think, though, that the 12ECC is better suited to post '00 4.0L's with the coil packs. Better still, I'd recommend NGK ZF5YN's.

 

My jeep is a 99 so I have a traditional distributor ignition system. By "Old" I meant that those are what I currently have in my rig- the one in the picture I just had a spare of. My biggest concern is interference with the piston, but I would also like to know what having a "hotter" plug means thanks for your help!

 

Diodes?

There are no diodes in spark plugs. What part is that you think is a diode?

 

in my picture I thought it's that ceramic piece where the spark occurs and I'm showing 2 different sizes up. PleAse let me know the correct terminology

 

thats the insulator for the center high voltage rod.
id avoid any much longer than the stock old ones, ??

 

Agreed!

 

From what I read the new plugs are what's meant for your rig the ones you're running now are what was ran pre 99 the more I read the more confused I got a lot of conflicting info on the internet.

 

Attachment 303254

 

I use ZFR5Ns in all the Jeeps I work on.Even old Renix stuff.

The projected tip works as a hotter plug at low speeds and cooler plug at higher engine speeds.


Oh, it's electrode, not diode......

 

Ah, got it. Electrode, diode. We were all newbies once.

This should help on the correct terms.

 

ill take your word for it! My biggest concern for the longer ceramic insulation was interference. If you're using it on old Renix stuff then I don't see it being a problem anymore. I wonder what happened to make the plug type change for 99+!

 

Maybe they decided to go with a better spark plug than Chumpions.......