Someone please diagnose these plugs

ETAModel

ETAModel

Senior Member
Howdy. Been away a while, parked Ole Edgar about 2 years. Got him going again. I have about 1500-2000 miles on these spark plugs, decided to pull them and take a look.
Note, I had cleaned them with a brush before taking pictures.
My question is about the insulator surrounding the electrode. Plug 1(nearest to radiator) and 2 look OK, but 3 has a definite red tint to the insulator, and #4 has more then 1 and 2, but not as much as 3.
What's going on here?
I'm waiting to install them based on your responses. I'm thinking about swapping 3 and 4 for 1 and 2.
Thoughts?
This is not a point car, only a driver. These are Autolite plugs.
 
Pics
 

Attachments

  • 20260810_122833.jpg
    20260810_122833.jpg
    43.8 KB · Views: 29
  • 20260810_123432.jpg
    20260810_123432.jpg
    47.6 KB · Views: 29
  • 20260810_123944.jpg
    20260810_123944.jpg
    26.4 KB · Views: 32
  • 20260810_124036.jpg
    20260810_124036.jpg
    25.3 KB · Views: 27
Run them again for a while, then post photos prior to cleaning them if you’re still concerned.From the looks of things I see nothing wrong
 
I'll check the gap and stick em in. I'd ask for opinions on plug gap, but I don't want to start a war!
 
Plug cleaning equipment that were used in the day used a sand blast. I would be a little leery of using a wire brush to clean them on fear of putting a metal deposit on the insulator. But I may be just a little too leery.
 
Full disclosure. I lost a nut holding the carburetor to the intake last week while on a drive and it sputtered, backfired, and bucked all the way home, about 10 miles. The only way to keep it running was to crank open the GAV almost 2 turns. I decided to clean and kit the carb while it was off.
I then decided to pull the plugs and clean them. They all were heavily sooted, as I expected. What concerned me was how Red the insulators were on the rear cylinders. The front 2 not so much.
 
nkaminar said:
Plug cleaning equipment that were used in the day used a sand blast. I would be a little leery of using a wire brush to clean them on fear of putting a metal deposit on the insulator. But I may be just a little too leery.
Click to expand...

Not having a sand blaster dad would soak them in gas then brush them clean. I tried to stay away from the insulator.
I know dealerships used sand blasters, as did the military. But i don't have that option, and I'm guessing many A owners don't either.
 
Both my father and my Father in Law would grind an old hack saw blade to a long point and use that to scrape/gouge carbon out of th depths of an old plug. I still do it.
IMO, 2,000 miles on a set of plugs is nothing. I used to run TT10s when they were available and only changed one set (at 75,000 miles). Sure, the motor ran better with the new plugs but I think even pulling them just have a look if there is no problem is a waste of time.
 
Last edited:
Your plugs look all good. The discoloration on the insulators could be from a small amount of coolant or oil leakage in their respective cylinders. If there is leakage it could be oxidizing during ignition causing the discolorization. Change plug positions and see if the discolorization repeats.
 
CT Jack said:
Your plugs look all good. The discoloration on the insulators could be from a small amount of coolant or oil leakage in their respective cylinders. If there is leakage it could be oxidizing during ignition causing the discolorization. Change plug positions and see if the discolorization repeats.
Click to expand...

Thanks, I was thinking of swapping them or and see if the red stain appeared again. I haven't used antifreeze since I installed the plugs.
 
Back when leaded gas was common, the plugs would run a nice medium brown color. The change to unleaded affected normal color from light gray to a bit of a yellow tint.

The insulator ceramic has a tendency to wear a surface porosity that catches anything that doesn't burn off easily. Stuff in fuel and oil can affect the insulator color depending on what it is. There are additives in both. Fuel additives vary depending on what the bach plants mix in for each customer. Spark plugs are generally grit blasted using any number of different abrasive materials and that just adds to surface porosity of the electrode insulator.
 
Your plugs look fine to me. As far as cleaning, I use non-chlorinated brake parts cleaner and a new (stiff) tooth brush. Re-gap them, install and enjoy the drive.
 
You must log in or register to reply here.
Back
Top