2005 Jeep Cherokee Limited with 5.7l Hemi. Bought plugs from Advanced Auto. OEM replacement Champion RE14MCC4. Pulled old plugs. They are Champion RC12MCC4. Considerable difference. See photo. Don't know what to do. Is it possible that the old plugs were just the wrong ones? All resources, Advance Auto, Autozone, Champion website and dealer all say to use RE14MCC4.

2/20/2012 1:46:32 PM

you should be fine, the one on the right is what comes up in http://www.rockauto.com's catalog

2/20/2012 2:01:35 PM

whoa there...

left plug is shorter and has crush washer

right plug is longer and has tapered sealing surface.... big fuckin' difference all things considered


Are the currently installed plugs truly incorrect?

2/20/2012 2:06:52 PM

perhaps the previous ones were packaged incorrectly

it happens

2/20/2012 2:09:33 PM

so i did a little more digging. the 4.7L calls for the RC12MCC4 plugs but the Hemi, which I have calls for the RE14MCCA4 plugs. going to go forward with the plug swap, cross fingers and fire her up. maybe this is why i'm getting such poor gas mileage and hesitation off the line.

2/20/2012 2:17:32 PM

that would be my guess

2/20/2012 2:23:25 PM

Could the old plugs have caused any damage to his engine?

2/20/2012 2:39:53 PM

being that they are shorter i don't think any damage was done. all i've noticed is that there is some residue on the threads inside the block for the last 1/2" of threading where the other plugs didn't thread all the way down. it almost loos a bit rusty. i'll snap a pick and post it shortly. it also gets a bit harder to thread in the plugs the last 1/2" due to the build up. i'm having to be very careful to get it seated correctly with out over torquing the plugs.

2/20/2012 2:51:20 PM

^gotcha

it's a wonder those crush gaskets didnt distort/break in the tapered seat.


good news is that thing's going to have some hella power now

2/20/2012 3:00:40 PM

this is the residue i'm talking about. the last few turn when tightening the plugs there is a lot of resistance probably due to this rust looking residue on the threads where the old plugs didn't thread all the way down before bottoming out on the crush washer.



about to start him up...will report back.

2/20/2012 4:26:23 PM

completed the plug swap and started him up. prrs like a lion. all is well. hoping to see a significant increase in gas mileage.

2/20/2012 4:42:25 PM

....Copper anti-sieze is also your friend (and will be your friend in a few years when you go to change plugs again)

2/20/2012 4:44:48 PM

i looked into that but evidently Champion recommends not using anti-seize. i debated either way but decided not to. i figured it's nothing a breaker bar can't take care of.

2/20/2012 4:55:22 PM

Quote :

"Here's what Autolite says about using anti-seize (snicked off the net somewhere): We do not recommend the use of any anti seize products for installing spark plugs. Anti seize compounds are typically composed of metallic, electrically conductive ingredients. If anti seize compounds come in contact with the core nose of the plugs, it can lead to a misfire condition. Anti seize compounds can also have a torque multiplying effect when installing plugs. This can lead to thread distortion and thread galling resulting in cylinder head damage. Autolite spark plugs are nickel plated to resist the effects of corrosion and seizing. However, plug seizure is aggravated further when steel plugs are installed into aluminum cylinder heads for a long period of time. Here's what AC/Delco says: Do not use any type of anti-seize compound on spark plug threads. Doing this will decrease the amount of friction between the threads. The result of the lowered friction is that when the spark plug is torqued to the proper specification, the spark plug is turned too far into the cylinder head. This increases the likelihood of pulling or stripping the threads in the cylinder head. Over-tightening of a spark plug can cause stretching of the spark plug shell and could allow blowby to pass through the gasket seal between the shell and insulator. Over-tightening also results in extremely difficult removal. -- heres the Pelican Parts explanation " Install each plug into the cylinder heads without using any anti-seize compound. Torque the spark plugs to 25 Nm (18.4 ft-lbs). While writing "How to Rebuild and Modify Porsche 911 Engines", I discovered that Porsche doesn’t recommend the use of anti-seize compound, as detailed in Porsche Technical Bulletin 9102, Group 2, identifier 2870. The bulletin applies retroactively to all Porsche models and the theory is that the anti-seize tends to act as an electrical insulator between the plug and the cylinder head. This could have detrimental effect on the firing of the spark due to the loss of a good, consistent ground connection. Keeping those findings in mind, I would make the same recommendations for the BMW cars." "

http://forums.bimmerforums.com/forum/showthread.php?t=1209753

I've never used anti-seize because of these types of recommendations against it. Haven't had one stick too bad yet. I might sing a different tune if it ever happens, but I'm doubtful it will ever happen.

[Edited on February 20, 2012 at 5:27 PM. Reason : l]

2/20/2012 5:26:27 PM

^i've read the same thus why i didn't use the anti-seize compound

2/20/2012 7:29:52 PM

Doesn't the hemi have 16 plugs ? ( my moms does in her 300 )

2/20/2012 8:04:24 PM

learn something new every day



I have bought plugs with anti-sieze from the factory.... who knows

2/20/2012 8:34:30 PM

I just can't buy it. We use anti-sieze in our industrial valve bodies and instruments every day and I know this is a little different application, but I'd rather have a possible poor ground that I can clean up instead of a stripped plug thread or snapped plug. The mfg's argument for galling goes completely opposite of the purpose that anti-sieze is used for. The argument for one mfg says it acts as an insulator due to its properties, another says it would be considered conductive. The only disadvantage of using it could be using waaay too much and leading to the short/poor grounding as they mentioned, and if that occurs you can wipe it down and reinstall, not get stuck up shit creek without a paddle or usable cylinder many miles down the road. As for torque multiplying, just use common sense on how much torque to use when using anti-sieze or retorquing them, most specs I see are less than 40 ft lbs and usually something just slightly more than what most people say is snug would be fine. There's even some resources I've seen giving an equivalent torque when usingdifferent types of lubricants.

2/21/2012 12:30:14 AM

My anti-seize is conductive... the only thing i would really worry about is a spark plug is the last thing you want to have backing out on you and anti seize would be conducive to that. I was having a hard time deciding if i wanted to use it on my headers, up-pipe and down pipe... and to be honest... i know i didn't use it on the turbo but that's the only thing i'm sure of.

2/21/2012 8:18:36 AM

after a sleepless night of back out all the plugs, yes all 16, and put anti-seize on them and this is why. you saw the last picture I posted right? there is combustion residue on the bottom of the plug housing where the shorter plugs didn't cover the threads. well i'm very concerned that after some time this residue will in fact cause the plugs to seize. I don't want to take that chance. normally i wouldn't use anti-seize compound but in this case i'm going to make an exception.

2/21/2012 8:36:40 AM