Spark plug color
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Is that a stock spark plug with the stock heat range? I can't claim to be a spark plug reader, but this is where to start.
The idea generally is to first optomize the air fuel mixture using stock plugs, a very common error for example is to install a hotter plug to compensate for excessive fouling due to an over rich fuel condition because of a misadjusted carburetor. In this case the correct procedure is to remedy the over rich condition versus installing a hot plug.
Performance engines use a colder heat range, etc. For most of us, stock spark plugs in stock engines are perfect. Just some background thoughts for you, maybe you know this stuff already.
The idea generally is to first optomize the air fuel mixture using stock plugs, a very common error for example is to install a hotter plug to compensate for excessive fouling due to an over rich fuel condition because of a misadjusted carburetor. In this case the correct procedure is to remedy the over rich condition versus installing a hot plug.
Performance engines use a colder heat range, etc. For most of us, stock spark plugs in stock engines are perfect. Just some background thoughts for you, maybe you know this stuff already.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Reading plus on today's fuels is difficult about all can use it for is to tell you if it is running too rich, what traditionally would look to be too lean can be just fine today's fuels, especially ethanol laced ones burn very clean and do not leave anywhere near the combustion deposits of the gasolines of days gone by.. Yours look to be ok. With most of today's fuels, a stoichiometric air-fuel mix tends to leave plugs clean with little to no combustion deposits, a state in years past that would indicate an overly lean fuel-air mix.
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Fleet Mechanic
Joined: Jan 2014
Posts: 1,946
Likes: 118
....just as I found, almost as many opinions as responses. Check my post on the same subject in the 61-66 forum, “reading spark plugs”. I think I learned something in the process.
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Lead Driver
Joined: Oct 2018
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It's not rocket science. off white to tan is exactly what you want. the reality is as long as you're anywhere in the good zone there are better things to worry about.
https://www.onallcylinders.com/2012/...r-spark-plugs/
https://www.onallcylinders.com/2012/...r-spark-plugs/
Posting Guru
Joined: Nov 2011
Posts: 1,302
Likes: 5
From: Burlington, WI
440 is spot on. That plug looks fine. If the other 7 look that good, run it and be happy. It's not quantum physics like some lead you to be believed, especially if you're just stuffing plugs in a stock motor. Even then of you're off a heat index or so, or if the plugs aren't perfectly colored (but still close), as long as they all look alike and have a decent gap you're fine.
Lead Driver
Joined: Oct 2018
Posts: 7,896
Likes: 2,372
Gas isn't that different. that's why it still works in 100 year old engines. if a plug looks as good today in a 428 CJ as it did in 1969 you are just as good to go now as you were then.
octane is a factor on some engines, the loss of lead is a problem if you don't have hard seats. but we still find our jetting and set our idle speed the same as we always did.
octane is a factor on some engines, the loss of lead is a problem if you don't have hard seats. but we still find our jetting and set our idle speed the same as we always did.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Gas isn't that different. that's why it still works in 100 year old engines. if a plug looks as good today in a 428 CJ as it did in 1969 you are just as good to go now as you were then.
octane is a factor on some engines, the loss of lead is a problem if you don't have hard seats. but we still find our jetting and set our idle speed the same as we always did.
octane is a factor on some engines, the loss of lead is a problem if you don't have hard seats. but we still find our jetting and set our idle speed the same as we always did.
Your're kidding right?
Gasoline is NOWHERE near what it used to be when these trucks were new. Not counting the 40 years of advancement in refining technology with the addition of active feedback computer control and much much tighter quality control.
Sulpher is now all removed, there is no lead and no lead replacements are used, the number of heavier chains leftover in gasoline from refining has been cut by 99%, hence the huge reduction varnishes and gums and combustion deposits, Additionally a whole cocktail of additives are used in modern gasoline. ignition promoters, anti-knock additives combustion improvers, oxygenators, atomisation enhancers, moisture dispersants, anti-corrosion additives and even the viscosity of modern gasoline is much thinner than gasoline of old. And that does not even count the addition of Ethanol that has a whole host of additives that go along with it. 40 odd years ago you got straight gasoline maybe with some TEL or MMT added. Today's gasoline bears little to no resemblance to the gasoline used 40 odd years ago, in fact, the only similarity is, it is called gasoline.
Lead Driver
Joined: Oct 2018
Posts: 7,896
Likes: 2,372
Yes it's amazing they both still burn isn't it ?
we're not talking about the chemical composition here we're talking about function. give me a break. any gasoline engine made from the model T to a new GT500 will run on the fuel we have today provided the octane required is provided. and hell they'd still run just not as good.
For all practical purposes the fuel we have today functions the same and it's up to us to tune and modify to make it work. and we can. and part of that is jetting . and that requires checking plugs which really hasn't changed at all.
If all of this blows you away and you can't adapt to the new fuel composition without such drama I hear the electric cars are getting better . maybe you should try one.
we're not talking about the chemical composition here we're talking about function. give me a break. any gasoline engine made from the model T to a new GT500 will run on the fuel we have today provided the octane required is provided. and hell they'd still run just not as good.
For all practical purposes the fuel we have today functions the same and it's up to us to tune and modify to make it work. and we can. and part of that is jetting . and that requires checking plugs which really hasn't changed at all.
If all of this blows you away and you can't adapt to the new fuel composition without such drama I hear the electric cars are getting better . maybe you should try one.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Yes it's amazing they both still burn isn't it ?
we're not talking about the chemical composition here we're talking about function. give me a break. any gasoline engine made from the model T to a new GT500 will run on the fuel we have today provided the octane required is provided. and hell they'd still run just not as good.
For all practical purposes the fuel we have today functions the same and it's up to us to tune and modify to make it work. and we can. and part of that is jetting . and that requires checking plugs which really hasn't changed at all.
If all of this blows you away and you can't adapt to the new fuel composition without such drama I hear the electric cars are getting better . maybe you should try one.
we're not talking about the chemical composition here we're talking about function. give me a break. any gasoline engine made from the model T to a new GT500 will run on the fuel we have today provided the octane required is provided. and hell they'd still run just not as good.
For all practical purposes the fuel we have today functions the same and it's up to us to tune and modify to make it work. and we can. and part of that is jetting . and that requires checking plugs which really hasn't changed at all.
If all of this blows you away and you can't adapt to the new fuel composition without such drama I hear the electric cars are getting better . maybe you should try one.
Today's gasoline have presented a pile of issues with older vehicles. Jetting is not really even the issue at all as the specific gravity and BTU content is relatively close. Not only can you NOT use reading plugs as an accurate guide to fuel-air mix short of extremely rich due to the combustion modifiers additionally EGR function will give false spark plug readings short of WOT operation.
The evaporation point of modern fuel point is much lower due to the lack of heavy's in it, modern fuels are designed for use in closed pressurised fuel systems. And this had presented a whole host of issues in carbed vehicles designed for older formulas of gasoline. This is why vapour lock and carbs going dry after shut down has become an issue.
To say the fuel is the same stuff because it burns in an engine is incredibly ignorant. Fricken Kersone will run just fine in a spark-ignition engine that does not make it gasoline or the same as what sold in the pumps 40 years ago.