Judging by your signature, you have a 98 (?). If so those are the wrong plugs for your motor. Those look like NGK FR5-1 plugs. You need ZFR5N plugs. FR5-1 plugs are the wrong plugs for a 4.0 of any year. NGK is dicked up on their website catalog.

Looks like you have a good clean burning FA mixture, based on the pic of one plug.

Good job of not using anti-seize on those plugs....oops, you said you put anti-seize on the plugs when you reinstalled them. Bad boy.

 

Data, Data, Data....

http://spark-plugs.co.uk/index.php/c...ntents.symbols

Concerning heat range: The NGK ZFR5N plugs have a heat range of 5, Champion RC12ECC have a heat range of 12. Becuse manufcturer's have different heat range coding, the NGK is just the opposite of Champion. The 5 and 12 heat ranges do match up...sorta. The NGK 5 is the equivalent of Champion 11 (or so), so they are just a hair cooler than the Champions. This could be the reason Chrysler went with the NGK ZFR5N plugs in their waste spark 2000/2001 ignition sysytem.

 

Thanks. I was kinda down in the dumps because my Champions had huge gaps, but this post really cheered me up.

 

Just an FYI the no anti seize advisory only applies to NGK at this time as they coat their plugs. Most others do not. General Motors for years has said to lubricate with synthetic oil vs anti seize. Other than that I have not seen anything from the other plug manufacturers.

 

Oops-Peaked my interest-Are you supposed to lubricate plugs when you install them? I can't remember ever reading that. Aren't you trying to maintain electrical ground with head so putting oil on the threads might cause poor contact. I could see anti-seize lube as it has metal particles in the fluid.

 

I really doubt it makes much difference. And the oil will shear on the thread contact so I doubt enough resistance would be introduced to matter

 

You can tell that without seeing the number? It's been a really long winter in MI, hasn't it.

 

This post comes from someone who shows he does not know "Jack *****" about spark plugs. When I went to the track I always had 3 different heat ranges of plugs, with spares for each one way of tuning engine. There were not cheap off the shelf plugs but race plugs meant to be used with high powered ignition setups like "MSD'. Plugs were pulled after every run and read to see what needed to be done with the carb. (jetting), timing and cleaned using a air compressor type cleaner with sand. If they were fouled in the least I should have said.

You need to just watch some of the posts as I do closely because of my lack of knowledge about Jeeps period. All I know is a little about SBC's, racing and a love of cars for over 50 yrs! Note I said CARS not Jeeps.

 

Long indeed!

 

Jeezz I poste before I read the whole thread and saw he had left, oh well to bad so sad.

A short answer on the anti-seize yes it needs to be done "IF" your putting the plug in an aluminum head because of the different materials. On race engines in the high dollar "Stock Class's" they put one drop of oil on each plug (cast iron heads) and then torque it down to spec. so the CC's are all alike in CC's in the chamber.

 

Thanks.

 

How are the Bosch copper top plugs?

 

Why do you ask?

 

CuZ O Rielys has them and from what I've read copper is the way to go so I figured I'd ask. They didnt have any NGK but idk about any other place

 

Thanks for the info. What is the harm in continuing to run those plugs? You were right on the money about them. That's what was in there when I bought it. Like you said, looks like it's been burning well. I'll know now not to use the anti-seize anymore.