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Meat Popsicle
91 CRX Si
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2,939 Posts
Discussion Starter #1
So I've read two different things in regards to identifying whether your plug is too hot, too cold, or ideal. Some sources say that you should use the ground strap plating discoloration to determine if the plug is too hot:



Others say to use the discoloration on the threads:




What method would you use?

Here's one of my plugs that has about 100 miles on it:



If using the second method, it would seem that the plug is too hot because the discoloration is about 5 threads up.


Here's a fresh plug that I swapped in that had less than two miles on it:




There's hardly any coloration of the threads but the ground strap discoloration is very near the threaded portion of the plug.


Any input is appreciated
 

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5,884 Posts
Looks like I am popping my plugs out this weekend. curiousity bites my asshole once again.


Thanks for helping me waste more time on my days off lol :fingersx:
 

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Meat Popsicle
91 CRX Si
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2,939 Posts
Discussion Starter #5
Wow, I would have expected more input on this topic. I'm guessing that there aren't really hard fast rules about it?

I know there's a relatively wide range between cold fouling and pre-ignition so I'm guessing as long as you're not hitting either of these points, there's no point in adjusting the heat range?
 

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Brokedick Millionaire
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40,425 Posts
Reading plugs is an art that you must learn hands on. Ever watch the NASCAR guys read them? When they switched to EFI last year, reading the plugs changed a bit.
 

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504 Posts
I have always used the 2nd pic for plug temp. And read the ground strap for timing. Too close to the tip, not enough timing, all the way around the corner, too much timing. Plug heat range can be a few different ranges depending on how much timing you have, and fuel used. There are a lot of factors into closing the right plug. For safety factor, you can't go too cold of a plug. Granted, you may not have an optimal burn, and may gain some power by going a step hotter, but it won't blow your motor like having too hot of a plug would.
 
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