Spark plug readers

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Michael Siple

Michael Siple

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Looking for a little input - to read fuel the plug needs cutting , ground strap indicates timing , and some say heat range is indicated by the threads. Here lately I have a hard on for reading plugs. Pics are of the same new plug with 75-100 miles on it. Thanks for your input. -Mike

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Agree with above, but I’ll add your timing is one,two degrees safe. Cut a plug and have a look at the fuel ring. And if it were mine, I’d look for one step colder plug, you don’t have any color on the threads yet.
 
Pics aren't great, zoom in with clarity looks close like others said.. but it's a hotter plug you need not a colder one if you need one at all
 
TT5.9mag said:
Agree with above, but I’ll add your timing is one,two degrees safe. Cut a plug and have a look at the fuel ring. And if it were mine, I’d look for one step colder plug, you don’t have any color on the threads yet.
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You mentioned color on the threads, I looked this up and found nothing about it. How can thread color affect performance? I've changed many a plug and sometimes the threads were the same color as when I installed them sometimes a little darker.
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It’s actually heat in the shell of the plug. You want 2-3 turns of color on the shell if you are trying to make power.
 
“You mentioned color on the threads, I looked this up and found nothing about it. How can thread color affect performance? I've changed many a plug and sometimes the threads were the same color as when I installed them sometimes a little darker.”

@Dan the man i had to quote you this^^^way because of how you replied above. @Newbomb Turk nailed it in post 7, and I will add to his reply. Changing plugs and reading plugs are two entirely different things all together. Trying to judge the tune up by looking at a plug with thousands of miles on it at various loads and rpm is a fool’s errand. Reading a plug for tune up must be done on new plugs. You make a hit, shut the engine off and read the plug. The color of the threads I mentioned above has to do with heat range and dialing in the plug’s ability to dissipate heat. It has very little to do with performance but can have a big impact on detonation and drivability. When the heat range is correct (or close to it) you’ll see 2-3 threads down from the tip colored (dark) after a pull, or at least that’s how I was taught by people much much more intelligent than me.
 
That's an indicator of proper heat range people.

Selective agrees and likes, fan clubs confusing people, great...
 
Thread color does not indicate cylinder pressure. It gives you an idea if your plug heat range is close. 3-4 darker threads and you’re in the ball park. Not a concrete indicator.
 
That’s just silly, what changes the color of the threads? Throw the plug in the ocean and take a peek at it a mile down. No change, plenty of pressure, no heat.
 
Don't if it's the lighting in the photo, but the strap looks a bit white to me. That would be an indication that you are running a bit lean (or have a little bit of a hotter range plug), but I don't think by much. I don't know why everyone commenting can't straight up tell you that. The color you want to see is some very light golding or browning on the strap almost like the one I have in the photo.

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Your plug shows to much timing or to hot of a heat range. There should be a slight change in color right around the bend. This is a rule of thumb. I would not change anything without knowing what you are doing with it. Race, you just back off the timing and start making runs. Keep adding 2 degrees until you lose mph. Then back off 1-2 degrees. The reason people just can’t tell him is his pictures only show idle mixture and timing and I have heard and actually see it on my plugs. You can tell if the plug came out of an open chamber LA cast iron head. For WHATEVER reason the LA head creates small triangle shaped marks on the top of the ground strap. Like 3-4 little marks. Very weird, but have seen them on my plugs. Actually looking at your plug there may be a change on the strap. Hard to see
 
furrystump said:
Your plug shows to much timing or to hot of a heat range. There should be a slight change in color right around the bend. This is a rule of thumb. I would not change anything without knowing what you are doing with it. Race, you just back off the timing and start making runs. Keep adding 2 degrees until you lose mph. Then back off 1-2 degrees. The reason people just can’t tell him is his pictures only show idle mixture and timing and I have heard and actually see it on my plugs. You can tell if the plug came out of an open chamber LA cast iron head. For WHATEVER reason the LA head creates small triangle shaped marks on the top of the ground strap. Like 3-4 little marks. Very weird, but have seen them on my plugs. Actually looking at your plug there may be a change on the strap. Hard to see
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Maybe it could be timing or the heat range, but it's not that far off, so the tune is close, but yet we can be fooled by the lighting in the pictures making it look more white than it actually is.
 
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