Jeep Strokers

Attached is a pic of my #6 Spark plug - can anyone give me a guess as to why it looks like it does? Click the pic for a closer look...

After a WOT shutdown: white is lean, black is rich.

Look closer at the specks on it - does it look like detonation? is is detonation blacks specs?

Detonation can be black or silver specks. Silver specks are actually pieces of aluminum...very bad. That also looks to be a platinum plug and those run even hotter to self-clean making pre-ignition worse. I would recommend at least going to the factory coppers, but ideally contacting NGK and giving them the specs of your build so they can recommend the proper plug.

Don't run plats. No need for them and the engine does best with standard plugs. NGK gave me a part number for my build. I think its on here someplace.

Also, that plug doesn't look good. Is it only the #6 plug?

Have you been using any fuel additives?

This is the #6 plug but 3 others looked almost similar. They all had a slight variance of this one but this one had it going up the tip. I have aluminum pistons and no signs of silver specks - However before I got the engine timed properly it ran real lean and I noticed pits on the pistons. Once the engine was timed properly it ran stoich with a hint of richness. The last thing I did was installed the Accell coil pack and opened the gap to .055. I closed the gap back to .035 and cleaned the spark plugs a bit and will re-check them in about a week. These are the bosch plats and will go back to the champions. I have a WB AFR in line and it sits on 14.5 average. Engine seems to be running good but this pic just concerned me.

Cheromaniac wrote:Have you been using any fuel additives?

No additives, just running mid-grade (87) out here.

This happened to me in the cylinder Nº 2, never knew what might be.

Those are running WAY too hot and probably detonating like mad. What is your AFR? How long does it take for the plugs to look like that?

Are those splitfires?

My plugs were Bosch FR9HC
When removing it had about 3000 miles.
I never appreciated any anomalies or detonation.