Last year I found my old colourtune from gunson and reset my mixture as my plugs were black and the car was running rich - last weekend I took my plugs out to see how the Re set was after a few hundred miles and I must say the plugs look great -an easy and quick way to get the mixture to a good standard - plugs out of no 1 and no4 Cyl
Maybe a bit lean now?
Possibly. The plug colour looks ideal, though conventional wisdom passed onto this rank amateur is the XK engine prefers to run a tad on the rich side where operating temps are a bit lower. The base of the plug is sooty while the business end is tan coloured. Stand to be corrected.
Are these two photos of the same plug? The second looks ok, but the first looks lean - might just be the photo. Whether this means anything depends on the conditions of the test. If you ran the car hard, stopped the car quickly, and the strap is brown to the weld on gas, you are good. If this is after idling the car for any significant amount of time, it doesn’t mean much. Bottom line - tuning a car to proper mixture at idle with Colortune doesn’t mean that you are necessarily running proper mixtures at speed.
Hi Ron
When I colourtune the car I did it at different revs but the car was static… the original plugs I took out were black all over … the car did run well…
But could not help having a go with the colourtune …
Ran the car for 500 Miles ( normal driving) and then decided to look at the plugs
These are from cyl no1
And the other 2 pics are from fly no 4
I find that plugs are a bit lighter when the engine is correctly adjusted since ethanol appeared. (This based on FI cars which are adjusted bang on).
Just been looking on the net about spark plugs… my word, is there is a whole world of pictures and opinions.
However, found a site and there is more about reading your plugs than I could imagine.
So, the bits of info I have digested is its not just about the colour of the porcelain
• The “Ground-Strap” = Heat Range
• The “Plug’s Base-Ring” = Jetting
The “Porcelain” = signs of preignition/detonation
This is my interpretation… so could be wrong…so any help would be great – as I don’t want to damage my engine.
Looking at my plugs….
My Ground Strap looks to be changing colour on the bend - so this could be an indication that the plugs are running slightly to hot.
The Plug Base ring is black – this indicated the engine is slightly running rich – this I don’t feel is to bad a thing as I would prefer to run rich as to run to lean.
The porcelain is white with a few great brown deposits – indicating the ignition is ok.
I must say the car runs great and there is no pinking etc…
Does anyone else have pictures of the plugs to compare with?? – but would be grateful for more feedback… as its all a learning curve….
Marc
yes, I think you are on the right track. Ground strap appearance also varies with alcohol content of the fuel.
If your engine is stock and you have standard needles, your idle/unloaded tuning should translate to operation under load. A more confidence-inspiring approach would be to drive the car hard and bring it in fast, then shut it right down. When it cools off, check the plugs again. Ideally, this is done with new plugs, but I do it with used ones. If they still have the features you described, you are good to go. If you want to get more sophisticated, weld an O2 sensor bung into your exhaust downpipe and temporarily wire an air/fuel meter to look at the ratios under road conditions. It’s interesting! Poor man’s “rolling road”. However, don’t expect as consistent results as those who are writing about plug appearance in fuel injected vehicles. I agree with you about a bit rich on a carbureted car being desirable.
Hi Ron
I never guessed I would be so interested by the colour of spark plugs and what they can tell you, I now feel like I need to take them out of all my cars!
Will have a go at what you said and see the results.
Thanks for the reply
Regards
Marc
