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Aron Gleason
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I understand that. But since the car was running too lean before, I had to go up in primary main jets. Now cruising it's running rich. So I have to go bigger on idle air bleeds to get the cruise afr's up.
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dcala84141....
Thanks for the red X.
By the way, most of that post was
quoted straight from Holley's
trouble shooting web site.
So I guess you would disagree
with them also.
Thanks for the red X.
By the way, most of that post was
quoted straight from Holley's
trouble shooting web site.
So I guess you would disagree
with them also.
Aron Gleason
Well-Known Member
1STMP here's a plug I pulled after Saturday's cruise. Even so it may look lean, my afrs were low 11's to low 12's .
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Definitely a lean burn. What plugs are
you running?
Aron Gleason
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Ngk xr5
Geoff 2
Well-Known Member
Smart move running the '5' plugs. Most folks run plugs that are too cold. I do not agree that the mixture is lean. Really hard to tell by 'look' with all of today's different fuel formulations.
What size is the engine?
What size is the engine?
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Are you sure your wideband sensor hasn't gone bad?
Is that plug from after a part throttle cruise, or a hard run after which the engine was immediately shut off?
Aron Gleason
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Plug is from after a part throttle cruise
Aron Gleason
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440 .030 over
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At part throttle cruise, that plug looks
like it's running a tick hot.
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"Are you sure your wideband sensor hasn't gone bad?"
Well, I am on a cel phone...
The OP has stated from the start that
his problem is from part throttle cruise
to WOT. Standing start it'll light 'em up.
His stumble complaint leans towards a
lean condition.
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Agreed, and the plugs also show a lean condition. Which is why I wondered if that 11 AFR reading was accurate.
Aron Gleason
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A tick hot? What do you mean by that?
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Lean. Burning hot.
Aron Gleason
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Even if the cruise afrs are low 11's?
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Notice where the color change
on the grounding element is.
That color change should be
about half the length of the
grounding element and not
so close to the tip.
The plug is in the cold range.
Geoff 2
Well-Known Member
Look at the plug: the shell is black & sooty. I do not believe it is running lean based on the pic....& I would not change the heat range.
The popular theory about a colour change half way up the ground strap [ GS ] is misleading & inaccurate...for many reasons. The colour change comes about from the heating of the GS. GSs vary in overall length, thickness & most importantly the volume of metal in it. Obviously if it has less volume, it will heat up quicker....& the colour change will be in a different spot. Does not mean that the mixture is lean or plug is wrong.
Also affecting GS colour: position of the plug in the chamber & how much cooling the GS gets from the incoming charge. Another factor affecting colour is how far the plug body protrudes into the chamber.
The popular theory about a colour change half way up the ground strap [ GS ] is misleading & inaccurate...for many reasons. The colour change comes about from the heating of the GS. GSs vary in overall length, thickness & most importantly the volume of metal in it. Obviously if it has less volume, it will heat up quicker....& the colour change will be in a different spot. Does not mean that the mixture is lean or plug is wrong.
Also affecting GS colour: position of the plug in the chamber & how much cooling the GS gets from the incoming charge. Another factor affecting colour is how far the plug body protrudes into the chamber.
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NGK describes something very
different.
And they're the ones who make the plug. I would lean to taking their
recommendations, and I'm sure
they would know under what
conditions their plugs work best in.
The OP's pic of his spark plug matches
exactly what NGK shows on their site
as a plug in too cold of a heat range,
and they give an explanation as to why.
All the heat in the GS is concentrated
at the very tip, and usually no bigger
area concentration than the electrode.
It matters not how far that GS
protrudes into the chamber (it's
designed in) or it's clocked position.
The OP's plug is running on the lean
side as all gasoline charge to the
cylinder is not being utilized, hence
the carbin build up.
Last edited:
Geoff 2
Well-Known Member
I have two or three NGK catalogs. None of them describe the GS colouration as a means of determining heat range. Nor have I seen any other plug manufacturers [ not mechanics ] use that description.
The colouring of the GS is dependant on a few factors/variables, as I described in post #118, making it unreliable.
From NGK catalog. I know the writing is small but the GS colour is not mentioned in any of the captions
The colouring of the GS is dependant on a few factors/variables, as I described in post #118, making it unreliable.
From NGK catalog. I know the writing is small but the GS colour is not mentioned in any of the captions
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