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Author Topic: Reading spark plug colors  (Read 1610 times)

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Dieselman966

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Reading spark plug colors
« on: October 26, 2019, 09:25:53 PM »
I pulled some plugs today on my 352.  If I had to guess from what I've read they are running hot and lean.  Does any on here read plugs for tuning?
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427mach1

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Re: Reading spark plug colors
« Reply #1 on: October 26, 2019, 10:02:27 PM »
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Dieselman966

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Re: Reading spark plug colors
« Reply #2 on: October 26, 2019, 11:08:33 PM »
What causes the red coating? Is that from the ethanol in the fuel?
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GerryP

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Re: Reading spark plug colors
« Reply #3 on: October 27, 2019, 08:21:49 AM »
Red powdery looking coating is usually manganese.  You would find manganese is aftermarket fuel additives serving to raise octane.
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My427stang

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Re: Reading spark plug colors
« Reply #4 on: October 27, 2019, 10:37:58 AM »
Quote from: Dieselman966 on October 26, 2019, 09:25:53 PM
I pulled some plugs today on my 352.  If I had to guess from what I've read they are running hot and lean.  Does any on here read plugs for tuning?

Reading plugs is almost a waste of time if you are just swapping after running in a variety of conditions.  Load, mixture, timing, temperature, all is continuously changing.  If they are burning clean, and not melting/cooking the center, I'd just run them.

Knowing your mixture by reading plugs is really only effective after a WOT blast with an immediate shut down, and even if that is perfect, it won't look the same after driving around
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Dieselman966

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Re: Reading spark plug colors
« Reply #5 on: October 27, 2019, 11:33:58 AM »
Quote from: My427stang on October 27, 2019, 10:37:58 AM
Quote from: Dieselman966 on October 26, 2019, 09:25:53 PM
I pulled some plugs today on my 352.  If I had to guess from what I've read they are running hot and lean.  Does any on here read plugs for tuning?

Reading plugs is almost a waste of time if you are just swapping after running in a variety of conditions.  Load, mixture, timing, temperature, all is continuously changing.  If they are burning clean, and not melting/cooking the center, I'd just run them.

Knowing your mixture by reading plugs is really only effective after a WOT blast with an immediate shut down, and even if that is perfect, it won't look the same after driving around

Ok I was mainly worried about the reddish color on them. I didn't know if that meant something. From what others have said that is just an additive in the fuel and nothing to worry about.
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Falcon67

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Re: Reading spark plug colors
« Reply #6 on: October 28, 2019, 08:53:27 AM »
Also, unleaded fuel and high power ignitions tend to not color plugs like the "old days" of leaded fuel and points.  You can see color if running leaded race fuel, and you can get a reading on mix by looking into the header pipes - nice even gray color is a good sign.  Unleaded premium just soots everything up like cheap wood in a chimney. 
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