Spark plug reading
Thread Starter
Racer
Joined: Jul 2004
Posts: 408
Likes: 0
From: Buffalo NY
Spark plug reading
Can some one take a look at my spark plugs and give me an idea of how things look? The thing that looks off to me is the little pieces of what almost looks like slag on the electrode.
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Thread Starter
Racer
Joined: Jul 2004
Posts: 408
Likes: 0
From: Buffalo NY
If it is burning oil, its not enough to see in the exhaust. And I don't put enough miles on the car to really see it in the oil level yearly.
I always run 91-93 octane. It runs well, no misses. I think it was running lean last year, so I rejetted my carb to the stock setup. It is an Edelbrock 1901 that was still jetted way small.
I always run 91-93 octane. It runs well, no misses. I think it was running lean last year, so I rejetted my carb to the stock setup. It is an Edelbrock 1901 that was still jetted way small.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
These plugs look like they have been in for a while so that makes reading them harder. In general it looks like the heat range of the plug is too cool. They should be a lighter shade of brown. This could be caused by too rich, burning oil, (one in second pic on the left particuarly) and plug heat range too cool.
In general they don't indicate anything that would be a big problem just looks like mixture and heat range is less than optimal.
Whatever condition the car ran last in ie idle, cruise, WOT that is what will be reflected most on the plug. These plugs do not appear new so they reflect an average of the running condition that it sees with the last condition weighted the most. That was probably idle. So you may be rich in the idle circuit. Or your mains may be too big, hard to say without some new clean plugs and testing.
Here"s a few good articles on spark plugs.
http://www.carcraft.com/techarticles/spark_plugs_tips/
http://ngksparkplugs.com/tech_suppor...5.asp?mode=nml
http://www.wallaceracing.com/plug-reading-lm.html
In general they don't indicate anything that would be a big problem just looks like mixture and heat range is less than optimal.
Whatever condition the car ran last in ie idle, cruise, WOT that is what will be reflected most on the plug. These plugs do not appear new so they reflect an average of the running condition that it sees with the last condition weighted the most. That was probably idle. So you may be rich in the idle circuit. Or your mains may be too big, hard to say without some new clean plugs and testing.
Here"s a few good articles on spark plugs.
http://www.carcraft.com/techarticles/spark_plugs_tips/
http://ngksparkplugs.com/tech_suppor...5.asp?mode=nml
http://www.wallaceracing.com/plug-reading-lm.html
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
The thing that looks off to me is the little pieces of what almost looks like slag on the electrode.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: May 2006
Posts: 18,734
Likes: 2,582
The original plug was R43N but the current recommendation from AC Delco is R44XL which is one level hotter and has an extended tip. Is your engine modified in any way?
Last edited by MelWff; Aug 29, 2012 at 04:28 PM.
Thread Starter
Racer
Joined: Jul 2004
Posts: 408
Likes: 0
From: Buffalo NY
Not to my knowledge. I don't think the previous owner did anything to it.
Last edited by matthud; Aug 29, 2012 at 07:45 PM.
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
Looks like fuel fouling to me. I'd go to the next hotter plug first. If the tips don't clean up, lean out the A/F mix a bit.
Here's a very good guide on reading plug tips:
http://autolite.com/sites/default/a/...n/plugtips.pdf
Here's a very good guide on reading plug tips:
http://autolite.com/sites/default/a/...n/plugtips.pdf
Thread Starter
Racer
Joined: Jul 2004
Posts: 408
Likes: 0
From: Buffalo NY
I swapped out the plugs with R45XLS plugs, changed the points, rotor and cap, as the rotor and cap also had some slag build up on the edges. I reset the Dwell to 30*. Idle timing is set, I need to go through the process of setting up the timing to make sure its all in by 3500 rpm.
How long should I run the new plugs before I pull them and check them again? I ran for about 20 minutes, and pulled #2 but saw nothing on the plug.
How long should I run the new plugs before I pull them and check them again? I ran for about 20 minutes, and pulled #2 but saw nothing on the plug.
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
I swapped out the plugs with R45XLS plugs, changed the points, rotor and cap, as the rotor and cap also had some slag build up on the edges. I reset the Dwell to 30*. Idle timing is set, I need to go through the process of setting up the timing to make sure its all in by 3500 rpm.
How long should I run the new plugs before I pull them and check them again? I ran for about 20 minutes, and pulled #2 but saw nothing on the plug.
How long should I run the new plugs before I pull them and check them again? I ran for about 20 minutes, and pulled #2 but saw nothing on the plug.