View Full Version : Need a plug reading

01-23-2012, 08:34 PM
This coming Sunday I've got a private track rental to go to so I figured I would do some basics before hand. Changed the oil/filter, fuel filter, and new plugs even though the ones I took out were only like 2 months old and had 2 bottles on them. Anyway I pulled number 8 out and found this. Now mind you the motor has almost 150k on it and a 100k worth the spray. I know the the motor is tired but to me it looks like it could be sooner than later that I will have serious issues by looking at this plug. Also there was oil on the threads. Maybe Don could chime in on this one.

01-23-2012, 09:08 PM
looks like ash to me

01-23-2012, 09:41 PM

Ash - lean on fuel in that cylinder from nitrous? says caused from fuel additives. do you add anything?

01-23-2012, 10:16 PM
No don't add anything. Wondering if its from the oil adadditives? there was oil on the threads. But I did install new valve seals when I changed the cam last year.

01-23-2012, 11:16 PM
I had a plug that had some ash on it like that, and probably not coincidentally I think my car has bad valve seals. The electrode was not white like yours however, which would suggest excessive heat or running lean. I assume it's a colder heat range plug for the spray? If you just did valve seals and there's still evidence of oil it might be worth doing a compression check just to rule it out, although you might be down compression anyways from the life that motor has had.

01-24-2012, 12:17 AM
Oh I can almost be sure that the motor is down on compression and the rings are gettting worn.

01-24-2012, 12:35 AM
Back cylander isn't getting enough fuel common on nozzle systems just be careful or jet up a tiny bit more fuel

01-24-2012, 02:48 AM
oil burning can also cause detonation at high rpm. food for thought.

01-27-2012, 03:36 PM
rings are shot. But we know this. Pull 2 degree's of timing on the spray.