NGK 6061-10 Spark Plugs

Hi there,

I had a broken NGK 6061-10 Spark Plug on my Top Alcohol Dragster last weekend.
(BAD with PSI Supercharger) The ceramic was blackened
from the bottom to the top.

After that run we serviced the engine and everything was ok. I have put a new Plug
in it and in the next run the same happened again on the same cylinder.

Does anyone have an idea what the problem could be?

Thanks TIMO

 

Yes; you are getting oil in the spark plug relief cut in the head and it is transferring to the plug wrench and onto the plug porcelain. It arcs down the porcelain to the case and grounds out the plug. It actually cuts a groove in the porcelain. If you look inside the plug boot you will find it has carbon from the burnt oil and it too will be grooved/melted top to bottom.
You need to put on a new boot and check all the others as transfer of oil could be elsewhere. You need to be sure that there is no oil in the head recess and that the spark plug tubes are clean before you put the valve covers on. We would also brake clean the plug wrench inside regularly.
When we had this happen I had thought that the plugs were cracked and defective from NGK and sent them some only to discouver this oil issue was the actual problem.
Jeff Johnsen

 

Negativ. Everything was dry before and after it happened. The problem is somewhere else for sure...
Could the heat of the cylinder be the problem?

 

Spark Plugs

over-torquing the plug, same result.

 

Timo; after the run we had no evidence of oil either, I can only guess it was burnt up by the arc from the mag, but there was a huge carbon track on the plug and in the boot. I thought that the plug was cracked but when I looked closely it was not; it had a groove burned in it which was black with carbon from the burned oil, but no evidence of oil present.
You said that with everything clean it did it again and in my opinion, it is not likely that a different plug using the same wire and boot does the same thing without a track in the boot to start this over again in the exact same hole. I'm only trying to help with this comment but I'd sure bet if you change the plug boot it out for a new one the problem will evaporate. I have had this exact thing happen more than once and changing the boot and cleaning everything fixed it right then and there.
Jeff Johnsen

 

plugs

I had same problem changed boot fixed