What's With This Spark Plug?

[floorit426]

I just changed plugs, in the hemi. I've never seen the brown discoloration, on the porcelain, before. Does anyone know the cause of this?

[Chryco Psycho]

It is possible the plug was poorly made & leaking compression

[MoparLeo]

Yes, many times. How many of your plugs are like this and what engine are you running these on? All Mopars came factory with Champion spark plugs. My Gen III 5.7 still comes with Champions.

[floorit426]

The engine is just a stock compression 426 Hemi. This was the only one of the lot, that looked like this. I have run both Champion and Autolite, forever. Both brands seem to have always performed well, for me.

[gzig5]

Probably was manufactured incorrectly.  Every company puts out a lemon every now and then.  As long as your motor was running right and not backfiring and bucking, I'd replace them with the same or what ever you like and get on with life. 

[Brads70]

I've  had a plug blow out the porcelain  and electrode before. It left nothing but the threaded metal part in the block. Looks like your plug was about to do the same. Good catch!

Sent from my SM-A715W using Tapatalk

[Topcat]

I just changed plugs, in the hemi. I've never seen the brown discoloration, on the porcelain, before. Does anyone know the cause of this?

I pulled one of my plugs today.
Autolite 65. Same exact brown stain.

Should I upgrade to these?

https://www.summitracing.com/parts/atl-ar25?seid=srese1&gclid=CjwKCAjw2Jb7BRBHEiwAXTR4jT76uojb0l9hLNBMh_WEvH2TbHJnwNwnm1cN8Ez6psqYOIxLMV5OFRoCZnEQAvD_BwE

[njsteve]

I had the same issue on prior 426 hemis. It is cosmetic. The plug is fine. You may want to replace the spark plug tubes and O-rings. They seep oil into the tube where the plug sandwiches the end of the tube against the top of the cylinder head. The oil residue then gets on the outside of the plug and then burns/boils/evaporates off from the heat, which leaves that discoloration on the porcelain. When you pulled the plugs were any of them wet with oil on the outside but the terminal end was still oil free? Is the end of the spark plug boot oily? That's usually how mine would be when I removed them, when the tubes were leaking.

[RUNCHARGER]

I doubt there would be any benefit.

[njsteve]

Here's some old photos of my Autolites (that's all I ran in the hemi over the 25 years I had it) You can see the two plugs in the middle of the bottom row have similar "stains". Remember that the insulator is also on that area of the plug and the oil just seems to cook in that spot. You can see how oily the entire set is, when you take them out.

[Topcat]

 

I had the same issue on prior 426 hemis. It is cosmetic. The plug is fine. You may want to replace the spark plug tubes and O-rings. They seep oil into the tube where the plug sandwiches the end of the tube against the top of the cylinder head. The oil residue then gets on the outside of the plug and then burns/boils/evaporates off from the heat, which leaves that discoloration on the porcelain. When you pulled the plugs were any of them wet with oil on the outside but the terminal end was still oil free? Is the end of the spark plug boot oily? That's usually how mine would be when I removed them, when the tubes were leaking.

Nice brown color.

I use the sealing cups.

[njsteve]

YES!
They didn't have those sealing cups back when I had my Hemi(s).
:-)