I need some help reading these spark plugs, please

I have been chasing a vibration that comes in and out of the RPM range.I have had the clutch pack balanced, replaced the vibration damper/crank pulley and sealed the intake leaks. The motor is a 2004 GTO LS6 intake. After the intake leaks were sealed up everything ran much more smooth and the vibration was less but still there. It is at its worst around 3K RPM.
Here are pictures of the spark plugs they are NGK TR55 gapped to .40 they each have a burn spot on the insulator. Is that detonation/preignition, too hot of a plug? That would explain the vibration. Would regapping to a wider gap help? Or changing the timing?
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Yeah, I would agree it looks like preignition. Maybe try the T6 plugs to drop down a heat range.

Rich

They look glazed. Use a colder plug.

Thanks, for the replies. Would I need a colder plug because of a timing issue? These are the plugs recommended for this motor with the gap changed from .55 to .40 as recommended by GM to compensate for poor idling on the factory motor with a bigger gap.
I need to get this car tuned, right now it is running a mail order tune.

Just out of curiosity, are you running rubber or poly motor mounts?

I have poly mounts and a similar vibration (not sure how bad yours is) and i'm pretty sure it's just the way it is.

Not saying you don't need to change your heat range on your plugs, but it might not be related.

Poly mounts. I have read on various forums issues people have with poly mounts, so that isn't ruled out for the vibration. I gapped the plugs to .055 and it did seem better but the vibration is still there. It seems that everything I try makes it a little better, the next time I am in the store I'll get some TR-6's.
Porch, does your vibration happen up and down the RPM range? Mine does.

How are your TT bearings?

No, mine is just a harmonic in the 2200-2500rpm range.

You could also check out your harmonic damper and torque tube bearings as someone else mentioned, but spark plugs are a lot cheaper!

acorad wrote:How are your TT bearings?

The vibration happens at a stop with the clutch in, so no TT bearing issue. I replaced the vibration damper/crank pulley and had the clutch/FW/PP checked for balance. I started another thread specifically about the vibration that someone suggested it may be tuning, looks like they were right. Still could be the mounts. Would the new style motor mounts help?

Is it really noticeable throughout the car, or just the shifter when you touch it?

It can be felt through the seat and shifter. I have the thrust bearings at the shifter, Xschop SSK and heim joints for the shifter linkage on top of the transaxle, so the shifter is tight.

Frustrating.

You'd think with a balanced fw/pp/clutch all would be good. I tightened my motor mounts during my vibration odyssey a few months ago and it did help some but not completely. I still get some vibes in the shifter at speed, but I think that's my TT bearings as they've also gotten much louder over the past few weeks or so. So I'm going to pull the trans/TT for the second time soon. Oh well.

Wish I could be more help.