Reading spark plugs, not tea leaves.

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Model T Ford Forum: Forum 2014: Reading spark plugs, not tea leaves.
Top of pagePrevious messageNext messageBottom of page Link to this message  By Erich Bruckner, Vancouver, WA on Sunday, April 13, 2014 - 10:38 am:

These have been running in my car for over a year. What are they telling me?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chester Leighton on Sunday, April 13, 2014 - 10:48 am:

Normal burn. Mixture is correct. Doesn't seem to be burning oil. I know there is a dark oily/sooty area at the bottom outside of the plug but that is common and normal. If that area were white, it would indicate a lean mixture. The area inside the plug at the electrodes appears to be a light brown which is what it should be. If that area were white, lean mixture. If it were dark black or had a lot of build up then that would be an indication of rich mixture or burning oil. Have you done a compression test and if so, what did it show?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erich Bruckner, Vancouver, WA on Sunday, April 13, 2014 - 10:52 am:

I have not done a comp test, but it has plenty as it is a bit of a chore to crank it over by hand. I was very pleased with the looks of these plugs. This is with the modified NH carb I had been running. Will be curious to compare at a future time after running with the "new" Stromber LF.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Sunday, April 13, 2014 - 11:00 am:

They look pretty good as far as running. Good color where it counts. I see two that MAY indicate a problem.
#4 is running in some oil. Check the compression. if it's lower than the rest, could be rings. If not, intake guide may be over wear limit.
#3 looks like it could have antifreeze/water exposure. Could be the head gasket or a crack in one of the valve seats. It's still firing so the leak may be minor.

Probably has a rough idle but runs good on the road. Most owners would ignore the signs and keep going.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Keith Townsend ; ^ ) Gresham, Orygun on Sunday, April 13, 2014 - 11:20 am:

Erich-
My eye might be a little out of calibration, but the gap on #4 looks a little too narrow.

I concur the burn patterns appears very satisfactory.

All in all, they seem to be operating fine for a set of old worn out spark plugs. Being the nice guy that I am I'll trade you those old worn out spark plugs for a set of shiny new A-25s.

: ^ )


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erich Bruckner, Vancouver, WA on Sunday, April 13, 2014 - 11:28 am:

I must say, the images look more intense than the plugs in real life. #4 looks more oily in the photo, #3 has antisieze on it, no rust. Valve guides are fresh, excellent smooth idle.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erich Bruckner, Vancouver, WA on Sunday, April 13, 2014 - 11:29 am:

Keith, you are toooooo kind.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erich Bruckner, Vancouver, WA on Sunday, April 13, 2014 - 12:07 pm:

Here is a comparison from before I did the valves. #1 is on the right again.



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