Good evening.
Went to check plugs today and a couple things I have questions on. All 8 gaps on the plugs moved closer. I originally gapped them at .040 and I noticed that the gap closed up. What causes this to happen?

Also all plugs are clean except plug no 7. This plug has a soft white covering on tip. What would this be a sign of?

73 olds omega with 350.
Thanks Bill

 

I would think either the plugs are wrong for the application (tip is too fat into the combustion chamber) or there is a bunch of carbon on the piston. Either may cause contact with the piston and close up the gap. Other than that, I’m out of ideas.

 

It may help if you posted which plugs you have.