Help with Spark Plug analyzing?
Thread Starter
Le Mans Master
Joined: Jan 2000
Posts: 6,595
Likes: 1
From: Thornton CO
Help with Spark Plug analyzing?
Can someone tell me if these plugs look good or not? My car has a miss right now and I'm guessing it's the Opti but want to make sure these plugs look ok. All of them look like these:
Large image
Thanks!
Large image
Thanks!
Thread Starter
Le Mans Master
Joined: Jan 2000
Posts: 6,595
Likes: 1
From: Thornton CO
Originally Posted by ZylaRace
You can find a bad/dead cyl w/ plugs, but a inter miss,... typically you can't see that by reading the plugs.
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
Originally Posted by SilverBeast
Is it me or does the gap on those plugs look really big?
.035 to .040 should be good. Excessive gap will lead to excessive fuel consumption with poor performance.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
Curious as to what are these plugs?????
Brand/model/heat range?
How long in the car & what kind of driving??
Looks to me like the porcelien on the plugs are carboned over to the extent the spark might occasionally go over the surface rather than across the gap.....or least suck up some of the spark energy
In any event I think it is time that they be changed....lot of carbon build up, looks like some "puddling" on back side of ground electrode looks really strange...pinging??, some "melting" on center electrode..
What is your compression ratio......
Check this out..
http://www.densoiridium.com/howtoreadusedplugs.php
Looks like yours might be combination of carbon fouling & start of preignition damage??
In answer to your question, IMHO these plugs could well be related to some missing.......are they even the right plug for your modified engine???? Your A/F??? running a little rich..
Sorry I have more questions than answers, but hope it is some good food for thought...
Brand/model/heat range?
How long in the car & what kind of driving??
Looks to me like the porcelien on the plugs are carboned over to the extent the spark might occasionally go over the surface rather than across the gap.....or least suck up some of the spark energy
In any event I think it is time that they be changed....lot of carbon build up, looks like some "puddling" on back side of ground electrode looks really strange...pinging??, some "melting" on center electrode..
What is your compression ratio......
Check this out..
http://www.densoiridium.com/howtoreadusedplugs.php
Looks like yours might be combination of carbon fouling & start of preignition damage??
In answer to your question, IMHO these plugs could well be related to some missing.......are they even the right plug for your modified engine???? Your A/F??? running a little rich..
Sorry I have more questions than answers, but hope it is some good food for thought...
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Thread Starter
Le Mans Master
Joined: Jan 2000
Posts: 6,595
Likes: 1
From: Thornton CO
Let's see, I have 9.8:1 compression and I live at 5,000' + altitude which means I actually have a little bit less compression than that.
Plugs are NGK TR55-GP - stock heat range. I gapped them at .050 per my engine builders recommendation.
They have about 10,000 miles on them. AFR is right around 12.5:1 on the dyno.
The color on the plugs is actually a light tan though it's hard to tell from the photo's. I was getting knock awhile back (5,000 miles ago) but then tuned that out with LT1-Edit.
Car made 352rwhp and 368lb/ft with these plugs and tuning a year ago. Last time at the track it pulled consistent 13.3's @ 104mph (the track altitude is 5800' (not the DA either that was like 9600)).
Plugs are NGK TR55-GP - stock heat range. I gapped them at .050 per my engine builders recommendation.
They have about 10,000 miles on them. AFR is right around 12.5:1 on the dyno.
The color on the plugs is actually a light tan though it's hard to tell from the photo's. I was getting knock awhile back (5,000 miles ago) but then tuned that out with LT1-Edit.
Car made 352rwhp and 368lb/ft with these plugs and tuning a year ago. Last time at the track it pulled consistent 13.3's @ 104mph (the track altitude is 5800' (not the DA either that was like 9600)).
Thread Starter
Le Mans Master
Joined: Jan 2000
Posts: 6,595
Likes: 1
From: Thornton CO
Originally Posted by skateparkdave
.035 to .040 should be good. Excessive gap will lead to excessive fuel consumption with poor performance.
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
Originally Posted by Timmy!
I don't have the compression ratio for that gap, or at least that's what I've been told. Car gets 25+mpg on the highway and 18-19 in the city as long as I'm not playing around. I went on a 300 mile trip last weekend and actually got 25.8 mpg with the miss that is going on.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
[QUOTE=Timmy!] AFR is right around 12.5:1 on the dyno.
QUOTE]
I assume these plugs were pulled after a street drive, so car should be closed loop back......12.5 is good for wot..the pictures show them as black with a lot of black on the center electrode porcelien.....carbon build up there can screw up spark.....carbon on the metal base still looks to me like an indicator you are running too rich or ????
Look at the first plug in the second photo....what are the puddle marks on the outside of the ground electrode??????....
Also as an aside what kind of cam are you running??? Suprised you dropped to 9.8 compression when you stroked it.....assuming you have a stroked LT1...
Good luck, I am not much help, but as a minimum, IMHO, these plugs were ready to be changed out even tho the electrodes at the gap seem to look pretty good...
QUOTE]
I assume these plugs were pulled after a street drive, so car should be closed loop back......12.5 is good for wot..the pictures show them as black with a lot of black on the center electrode porcelien.....carbon build up there can screw up spark.....carbon on the metal base still looks to me like an indicator you are running too rich or ????
Look at the first plug in the second photo....what are the puddle marks on the outside of the ground electrode??????....
Also as an aside what kind of cam are you running??? Suprised you dropped to 9.8 compression when you stroked it.....assuming you have a stroked LT1...
Good luck, I am not much help, but as a minimum, IMHO, these plugs were ready to be changed out even tho the electrodes at the gap seem to look pretty good...
Thread Starter
Le Mans Master
Joined: Jan 2000
Posts: 6,595
Likes: 1
From: Thornton CO
I dropped the compression because the plan was to run a blower. The pistons are 9.5:1 but the heads were decked and the builder calculated it all to 9.8:1. It does look like it's running a little rich and I'm assuming that could be because of the miss.
I assume that the car wasn't running rich before the problem because it passed emissions on what they call a fast pass which is where it doesn't break a certain limit on the dyno. Very few cars get the fast pass. Also, in TTS Datamaster my BLM's are right on the 128 side or so (or were - need to test again).
I assume that the car wasn't running rich before the problem because it passed emissions on what they call a fast pass which is where it doesn't break a certain limit on the dyno. Very few cars get the fast pass. Also, in TTS Datamaster my BLM's are right on the 128 side or so (or were - need to test again).
