mods are in my sig. these plugs are maybe 3 weeks old with not even 400 miles on them. put in brand new went straight to dyno shop. 40 miles or so. ran on dyno maybe 6-7 times ran fine. ran on the bottle twice on the freeway since then and the second time around car misfired while driving and i pulled this out. one thing to note was i misshifted 3-2 over a month ago. what could have caused this before i pull the heads off. will do leak down test. and this is plug number 8. other seven are fine. they were gapped at 42

 

Definitely do the leakdown test, that is a very bad sign. One possible cause could be a piece of piston ringland..... Or it could simply be you bent the electrode when installing the plug and the car was able to fire for a while despite it.

 

the plug is sitting flat together. and im sure it was like that since i put them on. im also thinking how about valve float. be it im running the crane rocker arms with just the ls6 springs. if a valve drops it can touch the spark plug? you can actually see marks on the curved end of the electrode. not gouged <SP> just nicked

 

It's the nitrous. Most likely a tiny melted piece of piston bouncing around hammering the spark plug before being expelled. Check your tune. Is it running fine after a plug change?

 

I noticed that it is an NGK. Assuming that it has a tad colder spark. Is that a TR6?

 

Scary. I would pray you just botched the install...since it is #8 maybe it went in bent.

 

He must have had a hell of a time putting that thing in if it is bent down like that.

 

changing spark plugs is not hard. i do it almost every other oil change. they are tr6's. i went and changed all the plugs out again and still hesitating. i havent pulled out #8 to see if it got bent again.

 

The valve won't hit the plug....it can't. It would have to be the piston and/or part of the piston. Either one is a BAD sign. I'd do a leakdown, then pull the head.

 

Don't say can't.

It could (valve strike) but it would be a MESS.

Do a compression test and if you can, get a borescope and insert it in the plughole and look for damage.

Also, your picture of the plug shows some carboned threads near the tip.

Are you sure that the plug isn't too long?

My $0.02

 

oh the color is from anti sieze on the plugs. its hard to get a digi cam to focus on a small object. its a tr6 so its not too long

 

Well....can't assuming it's still attached to the valve stem, so if it did hit 'part' of the valve you're right it will be a mess.

 

It also looks like there's some black specs on the insulator (pics kinda blurry tho).....if they are, thats a big indicator of major detonation.

 

added few more pictures to clearly see the plugs. remember i drove it another three miles misfiring with the ses light blinking so it was dumping a hell of alot of fuel you could smell it out the back

 

I don't know man...not saying anything bad about the OP but I've read things on here that I never thought could be possible with the things people do to their cars. If it were my car, that would be one of the few times I hoped I screwed something up and bent the plug myself.

Any updates?

 

i dont see why people think its so hard to change these plugs is all im saying... but nah i got too ripped drinking this past weekend and did not do any tests but im hoping to get to it this weekend.

oh yeah i did change all 8 with no change.. still not running right.. got too lazy to take it out again to see what it looked like. i just hope heads are readily available when i order them

 

Tune.

Does the electrode look like it was hit???
My best guess...some NASTY detonation.

Mine did this to a plug with no damage to anything. Still had the detonation issue once the plug was replaced. Filled up with different gas and it worked itself out. Very odd. Basicly a fluke.

 

yes it did look hit you could almost see a slight coloration from when it got touched though so i dont know yet. too lazy no hurry i guess

 

In that case...leakdown. Boroscope.
Good luck.

 

my over due update... see for yourself