i cant really find any good info on the net on reading plugs,

what im mainly curious about is the mixture ring coloring and placement with todays fuels. Alot of the articles I find are either from the 70s or are for racing classes using race gas

Im using just regular pump 93 octane from chevron and im trying to get my mixture nailed
from all ive read they all speak of a dark mixture ring that forms at the base of the porcelain, and too dark is rich, light brown is good, too light is lean etc

Ive come to the conclusion that this cannot be so with pump gas, as my car isnt that far off and the plug cuts only reveal a very very light tan ring that starts pretty high up on the porcelain (im cutting the plugs) and extends pretty much all the way down

ive recieved some conflicting advice about this
most sources say there should be the ring down deeper like i described, another source says the very light tan should start in the middle of the porcelain Mine is about 75% the way up which would lead me to assume that im a little rich

this is a plug cut from 5800 rpm btw

i can feel/hear the engine get just a little uncomfortable (a normal person would not be able to tell it pulls strong just ive become intune with the sound of my motor when its healthy) around 5200 rpm and in my "jetting" (im tuning the eprom actually) I have it quite a bit rich there compared to the rest of the curve

ill need to get some more plugs to continue my testing but in the meantime can you tell me what i should look for with pump gas? is that light tan band what i should be looking for? and should it start lower.. like toward the middle of the porcelain?

any thoughts would be appreciated

 

I know what you mean. Reading plugs with modern pump gas is becoming lost art.

Here's my .02. Others may disagree but they're wrong.

Light tan on the tip of the porcelain almost right up next to the center electrode is what you are looking for. Forget about what's way down at the base of the porcelain- damned little combustion happens in that tiny little crevice as near as I can tell. Projected nose plugs are by far the easiest to read because of this.

That doesn't mean that you aren't running lean on the top end due to inadequate fuel supply or whatever. Plugs out of my 400 Malibu could have been put in a textbook under the heading "perfectly colored plugs" even though at the time my fuel pump was not keeping up at the top of every gear. It takes some time for plugs to color and unfortunately that's longer than a breif lean spot will indicate, usually.

And don't forget that unless you cut the engien clean at the end of a run and whip out your plug wrench you still have to consider that the engine is loading up the plugs on the return road at the strip or idling for who knows how long on the street before you get those plugs out.


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94 Firebird Formula M6- No options but Z rated tires. No mods over $10 and no more planned for now. 13.5 @ 105.
79 Malibu "beater" w/junkyard 400 SBC, tweaked QJet 4bbl, a few other tricks. A maddening 13.000001 @ 108 on the motor with little traction. All it's go-fast parts just yanked off to go on the OTHER Malibu...
Grandma's old 78 Malibu (33K miles!). Just built a fresh 383 short block, topping it off with the go-fast stuff from the other Malibu right now!

"One of the last remaining QJet tuners on Planet Earth!"

 

Im cutting them clean damon, brand new plug, 5800 rpm in 3rd gear so it loads for a bit, and then bam i cut the ignition, clutch in, and pull to the side and pull it out

"Light tan on the tip of the porcelain almost right up next to the center electrode is what you are looking for. Forget about what's
way down at the base of the porcelain- damned little combustion happens in that tiny little crevice as near as I can tell. Projected
nose plugs are by far the easiest to read because of this."

hmm hehe yet another bit of info


the spot im getting up by the tip is on one side of course and is a little darker than light tan, more of a brownish color
so i have that ring forming which is very light tan, about 75% up on the porcelain, and on one side of the tip i have a spot of dark brown (this is the shrouded side correct?)

deeeep down in teh plug it looks almost perfectly clean and yes im using R43ts regular run of the mill plugs

 

i'm inclined to agree with damon about the ring more outward towards the tip. it'd be hard to optimize your preformance on the street over a wide rpm range and a varity of conditions. are you haveing any preformance problems?

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ICON Motorsports
1st & 3rd

 

They get colored on one side more than the others for some reason. Near as I can tell it's totally normal. Mine do it, too.

If you're coloring up a fresh set of plugs with one 1/4 mile run you're almost certainly too rich. Mine take several runs to get any meaningful color at all. Light tan is what you are looking for, not brown. Brown is bad. Brown can also be rings on their way out, in my expereince. You dropping an extra quart in the motor every 800 miles for no explicable reason? Bad rings make plug color just about meaningless.

My 400 Malibu motor has exactly 3 cylinders with good ring seal and those three cylinders have plugs you could take home to meet your mother! The other 5 look great for about 300 miles- looking maybe jsut a bit "richer" then the rest before they load up with that familiar oily mess.

 

not really ede except for the car peters out before i think it should (could be the heads)

it really starts to go a little past 3000 and just snowballs right upward to about 5200 where it levels off and I eventually shift around 57 or so

ive become real intune with the exhaust note and it sings as it cruises past 4000 but i definately hear something slightly amiss around 5200 where it levels off

im pretty sure theres nothing mechanically wrong just a little bit off in my tune i think im rich but im trying to determine what exactly is a little rich reading plugs with the gas im using since it burns so damn clean

if what damon is saying about the spot on one side of the porcelain is true then im definately rich its a bit beyond tan more like a brownish dark color

its just that everythign i read keeps telling me the coloring for the mixture strength shows up deeper on the porcelain

course everything i read is either motorcycle articles for two stroke engines, or from the 70s, or for race gas drinking engines

 

ahh damon youve been most helpful

so you are saying the nose should stay pretty damn clean after one run? I have nother plug i pulled here from the mid 4000 range that doesnt have the dark brown spot it has a very very very light tan spot on one side of the tip.. and mid 4000 it runs killer

so its safe to assume im a little rich with that dark spot on one side after one run in 3rd to 5800

btw im literally cutting it out at 5800 and just coasting to the side so its about as clean as a cut you can get

 

hey damon... would you happen to have ICQ or AIM? id like to pick your brain on a few things

 

btt

 

Hey olbap, damon is an AOL user (look at his email) so you might catch him on IM.
...ed