Read These Spark Plugs
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Joined: Apr 2005
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From: Santa Clara CA
Read These Spark Plugs
92 LT1 w/ about 92K miles on the clock.
What do you think about the story these plugs are telling? I'm interested in any/all comments, but in particular I'm interested in your thoughts on plugs 6 & 8.
What do you think about the story these plugs are telling? I'm interested in any/all comments, but in particular I'm interested in your thoughts on plugs 6 & 8.
Le Mans Master
Joined: Sep 2009
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From: My interests are mobile
Completely impossible to read anything from those pics other than idle fueling. Anyone that tells you different doesn't read plugs correctly. Furthermore, reading old plugs isn't going to tell you much aside from the general condition of the motor. Such as if they are covered in oil, carbon fouled, etc. Truly determining the state of tune, ignition timing and heat saturation can't be determined by those pictures.
If anything it appears there's some variation between cylinders in terms of wear. 6 and 8 have carbon build up...kind of obvious.
If anything it appears there's some variation between cylinders in terms of wear. 6 and 8 have carbon build up...kind of obvious.
Last edited by RC000E; Sep 17, 2009 at 10:47 PM.
Thread Starter
Advanced
Joined: Apr 2005
Posts: 93
Likes: 0
From: Santa Clara CA
Completely impossible to read anything from those pics other than idle fueling. Anyone that tells you different doesn't read plugs correctly. Furthermore, reading old plugs isn't going to tell you much aside from the general condition of the motor. Such as if they are covered in oil, carbon fouled, etc. Truly determining the state of tune, ignition timing and heat saturation can't be determined by those pictures.
Too my non-plug-reading eye, cylinders 6 & 8 look to be on the rich side--perhaps unduely rich--at least under the conditions the plugs were operting under just before the last shut-down, which was normal around-town motoring. I'm hoping someone will see this and say, "oh yeah! Mine were like that too and it was caused by <insert ah-ha cause here>" or... "every set of plugs you pull from an LT1 will look like that under those conditions." I didn't state that in the beginning because I was trying to not lead the witnesses.
As an aside, plug one was under a no-spark condition for 20 or so miles due to the wire having fallen out at the opti. Knowing that, if you look at the pic of plug one, you'll probaby think "yeah, I can see that."
Le Mans Master
Joined: Sep 2009
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From: My interests are mobile
Well, your statement isn't really correct. Like I said, if you have a lot of miles on the plugs you really can't determine the most recent condition of the motor. Carbon build up will occur and will obscure what your attempting to see.
Plugs are generally read on 3 levels, idle/no load, part throttle/mid load and wot. Each phase is judged based on a different area of the porcelain...none of which you can even see in those pics. Ignition timing also cannot be determined because the ground straps aren't visible and have build up on them.
Like I said, the only thing you can really take from that is there is variation involved. This would lead to believe that your having less efficient burn in cylinder 6 and 8 versus the others. This is likely due to mileage, injector variations/wear...a multitude of things.
Plugs are generally read on 3 levels, idle/no load, part throttle/mid load and wot. Each phase is judged based on a different area of the porcelain...none of which you can even see in those pics. Ignition timing also cannot be determined because the ground straps aren't visible and have build up on them.
Like I said, the only thing you can really take from that is there is variation involved. This would lead to believe that your having less efficient burn in cylinder 6 and 8 versus the others. This is likely due to mileage, injector variations/wear...a multitude of things.
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
czissman,
How many miles on these plugs?
I'd offer up two thoughts.
1. plugs temp range is too cool, as it's not burning off any of the carbon.
2. if those are the bosch plugs, many have commented about then NOT working well.
Consider replacing with either stock ACDelco's, or if your worried about the 'pucks' falling off (platinum spot on ground-electrode), then consider the NGK iridium (might be TR55ix -- that's what I put into our 94 LT1).
How many miles on these plugs?
I'd offer up two thoughts.
1. plugs temp range is too cool, as it's not burning off any of the carbon.
2. if those are the bosch plugs, many have commented about then NOT working well.
Consider replacing with either stock ACDelco's, or if your worried about the 'pucks' falling off (platinum spot on ground-electrode), then consider the NGK iridium (might be TR55ix -- that's what I put into our 94 LT1).
Le Mans Master
Joined: Sep 2009
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From: My interests are mobile
I disagree with that. Possibly going to a brand that works better is good advice, but playing with heat ranges based on two to three plugs is not good advice. Several look to be burning well and self cleaning well. Going hotter could merely serve as a band aid yet could also increase potential pre-ignition in the healthier cylinders.
Check plug wires for cracks or signs of degrading quality and replace the plugs and monitor...that's the best option. Go with a spark plug brand more popular with other enthusiasts also. Don't play with heat ranges based on those pictures.
Truly determining the proper heat range would require closer pics. I can't see the threads or the ground straps clearly enough.
Check plug wires for cracks or signs of degrading quality and replace the plugs and monitor...that's the best option. Go with a spark plug brand more popular with other enthusiasts also. Don't play with heat ranges based on those pictures.
Truly determining the proper heat range would require closer pics. I can't see the threads or the ground straps clearly enough.
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
I disagree with that. Possibly going to a brand that works better is good advice, but playing with heat ranges based on two to three plugs is not good advice. Several look to be burning well and self cleaning well. Going hotter could merely serve as a band aid yet could also increase potential pre-ignition in the healthier cylinders.
Check plug wires for cracks or signs of degrading quality and replace the plugs and monitor...that's the best option. Go with a spark plug brand more popular with other enthusiasts also. Don't play with heat ranges based on those pictures.
Truly determining the proper heat range would require closer pics. I can't see the threads or the ground straps clearly enough.
Check plug wires for cracks or signs of degrading quality and replace the plugs and monitor...that's the best option. Go with a spark plug brand more popular with other enthusiasts also. Don't play with heat ranges based on those pictures.
Truly determining the proper heat range would require closer pics. I can't see the threads or the ground straps clearly enough.
I wasn't suggesting to play with different heat ranges of the same brand/model plugs, just that the plugs look to be too cool and might be partly due to that brand/model of plug.
For example many have noted that the NGK's appear to be a 'hotter' plug than the ACDelco's.
However, to be clear, the appearance could also be weak spark issues, improper spark-plug torque, low octane fuel, fuel system issues, plug age, camera angle/flash strength, etc.
Here's a informative website information link:
http://www.ngksparkplugs.com/tech_su...d.asp?mode=nml
Last edited by theadmiral94; Sep 18, 2009 at 12:56 PM.
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Le Mans Master
Joined: Sep 2009
Posts: 6,937
Likes: 348
From: My interests are mobile
Exactly...there are multitudes of issues that could contribute to varying plug conditions pictured. That's why I say, go with a plug that's proven, check basic ignition system components and monitor the situation.
Pro
Joined: Jul 2002
Posts: 514
Likes: 0
From: ceres ca
St. Jude Donor '08
I'm sorry but I'm old school. Put in a set of normal plugs and try it again. If you have the same results, go back starting at the wires and find out why you have a weak spark. If this doesn't work PM me and I will explain why these plugs are a POS on our vettes.
Good luck
Randy
Good luck
Randy