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Discussion Starter #1 (Edited)
Ok, how to read plugs. There is A LOT to be read from plugs I'm finding out!

There are other areas to be studied on plugs after the pics, but here are some ways to quickly identify problems.....

Oil Fouled:


Carbon Fouled:


Too Cold:


Cold or Rich, but OK:


Good on Cool Side:


Very Good:


THE BEST:


Best:


Good on Warm Side:


Slight Hot but OK:


Hot or Lean but OK:


Too Hot or Lean:


Now, for more discussion...

#1 Is a timing indicator, you'll see a definite color change on the ground strap, it doesn't show well here but you can still see it right about at the arrow. Too much timing and the color change will be very close to the threaded body of the plug, too little and it'll be closer to the tip. Ideally we want it right in the apex or center of the 90 bend on the ground strap. This plug shows too much timing for the combustion chamber efficiency or octane level.

#4 Arrow shows another indicator of timing, you'll usually see a brown ring right at the tip of the porcelain area it should be a sharp and defined ring about .020 wide. Wider indicates not enough timing and any smaller , or only 1/2 way around or nonexistent as in this image is the second indication of too much timing in the motor.

#2 The tip of the ground strap is loaded with OIL deposits, fuel deposits are usually flat black in color and almost like a fine powdery deposit, this motor is leaking oil into the combustion chamber, bad valve guides, leaking valve covers allowing oil to seep through the plug threads, whatever it needs to be fixed.

#3 The threaded portion of the plug gives you the heat range, look at the threads you'll see that a few toward the tip are a dull burnt looking color the rest are black and shiny. You want about 2 threads showing the heat on the end of the plug and the rest of the threads to be shiny, this plug is impossible to read because of the oil mess. If you using a longer reach plug than this one 2.5 to 3 threads is optimum.
To increase the number of burnt threads increase the heat range of the plug, if you have 4-5-6 threads burnt you need to get a colder plug.


The plug is showing me by the deposits on the tip of the electrode and also the deposits right on the edge of the threaded body.
that it's slightly fat at idle.

The white porcelain is showing a lean condition at WOT, it's not too far advanced as the total timing mark or color change is right in the apex of the ground strap curve. The Idle timing is shown by the triangular hazing up on the flat of the ground strap and without even looking at the distributor specs I can tell you that the timing is about 18-20 initial and 34 total.

I would need a better picture of the threads to determine the heat range.

Changes:
I would try and lean it out just a touch at idle and up the jets by 2 points to fatten up the WOT circuit.

That slightly lighter color at the tip of the ground strap indicates too much gap, nothing serious but next time you change plugs I'd go to about a .036 gap from the current .040. Too much resistance caused by too wide of a plug gap can cause excessive heat on the tip which will shorten the life of the plug and really give you no benefits. I believe excessive plug gaps are not required on most Muscle and bracket cars, once you get into real big compression and major power you would open up the gap and replace plugs 2-3-4 times a year.

Compliments of FBO - http://www.4secondsflat.com/Spark_plug_reading.html

More info on reading plugs courtesy of Wallace Racing - http://www.wallaceracing.com/plug-reading-lm.html:
The "Ground Strap" = Heat Range
The "Plug's Base Ring" = Jetting
The "Porcelain" = signs of preignition/detonation

Heat Range:

Slightly Cold
Heat Range = Ground Strap, the ground strap indicates the heat-range of the spark plug. If the "color" of the ground strap "changes" too close to the ground strap's end, (which is above the center electrode), then the heat-range is "too cold" , meaning that the strap is loosing heat too quickly to the base ring, and is not able to burn off deposits until near its end. If the "color" of the strap changes near where it is welded/attached to the base ring (last thread ring), then it means that the plug heat-range is "too hot", because heat is not being tranferred/cooled from the strap to the base ring quickly enough !!!! The strap might begin to act like a "glow-plug", eventually causing preignition and/or detonation later on. Proper heat-range is when the "color" is at the half-way point on the strap, neither too cold or too hot.

(Color= meaning the evidence of heat/or lack of heat by the appearance dark vs lightened color of metal)

Spark Plug Firing Order:

 

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Wow....great post! I knew you could tell a lot about how an engine is performing just by looking at the plugs but not this much. This is a good one thanks.
 

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Dude, you've posted some awesome stuff, but all the pix in this but the last one are carb engine plugs.

Our V8, obdII engine's plugs will probably never look like that.

We should collect some pix from members; a lot of people here have widebands, and regularly check their plugs, and can probably even tell you what the average lambda was over the plugs life. :)

I could for one car... But I'd have to pull the plugs and photo them. With my schedule, that will happen the next time the intake leaks, lol.

I do need to check the plugs in the tbird; it's all stock, less than 100k miles.

I'll photo them, and see if I can get a good datalog. To get the wideband in, I'll have to remove a rear o2 sensor; as this one isn't tuned, it may complain.
 

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Discussion Starter #4
Dude, you've posted some awesome stuff, but all the pix in this but the last one are carb engine plugs.

Our V8, obdII engine's plugs will probably never look like that.

We should collect some pix from members; a lot of people here have widebands, and regularly check their plugs, and can probably even tell you what the average lambda was over the plugs life. :)

I could for one car... But I'd have to pull the plugs and photo them. With my schedule, that will happen the next time the intake leaks, lol.

I do need to check the plugs in the tbird; it's all stock, less than 100k miles.

I'll photo them, and see if I can get a good datalog. To get the wideband in, I'll have to remove a rear o2 sensor; as this one isn't tuned, it may complain.
Sure, but fuel is fuel no matter how the plug fires it, right? Maybe our FI cars won't ever show such drastic plugs, but with more and more people doing their own tuning - I'm just sayin'!

I know I've personally seen almost all of these plugs come out of fuel-injected cars (and more I've shown in other threads with the tips GONE).

Very few people on this site have identical cars, also.....
 

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WOT Junkie and avid corn burner
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Anyone feel like reading these? lol They are from my '85 Mustang GT. Engine is the original. 5.0L H.O., 4 barrel 600 CFM carb. Original heads, cam, intake manifold. I have the base timing set to 15* BTDC. Vacuum advance is on manifold vacuum during warm up, on ported vacuum during normal, warmed up operation.

one bank:
<a href="http://imgur.com/4GNjO"><img src="http://i.imgur.com/4GNjO.jpg?1" title="Hosted by imgur.com" alt="" /></a>

the other bank:
<a href="http://imgur.com/cxO8h"><img src="http://i.imgur.com/cxO8h.jpg?1" title="Hosted by imgur.com" alt="" /></a>

the same bank, but turned over:
<a href="http://imgur.com/KNt8C"><img src="http://i.imgur.com/KNt8C.jpg?1" title="Hosted by imgur.com" alt="" /></a>
 

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Reading plugs is how Ive always dialed in nitrous setups.
 

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The Parts Guy
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Anyone feel like reading these? lol They are from my '85 Mustang GT. Engine is the original. 5.0L H.O., 4 barrel 600 CFM carb. Original heads, cam, intake manifold. I have the base timing set to 15* BTDC. Vacuum advance is on manifold vacuum during warm up, on ported vacuum during normal, warmed up operation.
Looks like it's burning oil on quite a few cylinders. Were you running any fuel additives recently (Stabil, Lucas, or any fuel treatment or octane booster)? It looks like there is a red tint on a few of the plugs.
 

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WOT Junkie and avid corn burner
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The only additive I've used is fuel stabilizer since this car sits for extended periods sometimes. It does use oil, it has over 250K on the clock. So the deposits are mostly from burning oil, right?
 

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The Parts Guy
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Yep, the ash deposits are due to burning oil, and the red tinge is due to the fuel stabilizer.
 

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Discussion Starter #11
I'm with racecougar, that is a TON of foreign deposits on those plugs including whatever is getting into the cylinders through the crankcase and whatever you're mixing in the fuel!
 

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WOT Junkie and avid corn burner
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I will say, these are the worst looking plugs I've personally seen. I put a new set in the other day. I rarely put anything in the fuel. This particular motor goes through a quart of oil every week or so of normal daily driving. Surprisingly, it doesn't smoke! lol
 

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PostSlut
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If I remember, I will snap a pic of my plug numbers, 1, 4, 5, and 8.
I melted them with too much nitrous on my 4.6L
 

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WOT Junkie and avid corn burner
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Installed a set of Autolite AR94's today. This is what the NGK TR6's came out looking like. On one of the electrodes, I noticed there was some small glazing.
<a href="http://imgur.com/5zgpWCB"><img src="http://i.imgur.com/5zgpWCB.jpg?1" alt="" title="Hosted by imgur.com" /></a>
 

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The Parts Guy
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It's hard to tell for certain from that picture, but it looks like that plug is a little too cold for your application.
 

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Superlx30 said:
is it true the our 5.0 engines run better with copper ones?
I've been running Copper plugs for years in my Sport..

The engine just seems to run smoother with them.. :zdunno:

I think the only benefit to running Platinum plugs is you don't have to change them as often..



Rayo..
 

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I've been running Copper plugs for years in my Sport..

The engine just seems to run smoother with them.. :zdunno:

I think the only benefit to running Platinum plugs is you don't have to change them as often..

Rayo..
What I run as well .... copper is a better conductor even if the plugs do last shorter lives.
 

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Just put in a set of DENSO IRIDIUM TT, double tip plugs. Naturally any new plug should perform better than the ones replaced. I'm hoping these will perform better than copper and last many years. DENSO IRIDIUM TT
 
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