BIZARRE Spark Plug Color?
 

Changed the plugs in my 1973 Chevy C20 454 and found a interesting color on one plug! You can see from the pics below that one plug is yellow, and it's actually a brighter yellow than the pic shows. All the other plugs were normal, I even metered them all and they had proper resistance so what would cause only one plug to have such a crazy color?

http://i1137.photobucket.com/albums/...psbc440a72.jpg

http://i1137.photobucket.com/albums/...ps68b27b41.jpg

Re: BIZARRE Spark Plug Color?
 

would antifreeze happen to be leaking in that cylinder?

Re: BIZARRE Spark Plug Color?
 

Not likely because there is not antifreeze in the 454, just water. Could plain water cause it to turn yellow?

Re: BIZARRE Spark Plug Color?
 

Antifreeze would be my guess too. Plain water would wash it clean.

Re: BIZARRE Spark Plug Color?
 

Maybe he has the same space aliens messing with him that are always goofing around with me.
Or something causing that cylinder to run extremely lean .......

Re: BIZARRE Spark Plug Color?
 

Used to drive a c-60 with a 366 that was always overweight. It would make orange hue on the plugs. But not that

Re: BIZARRE Spark Plug Color?
 

http://www.circletrack.com/techartic...?__federated=1

According to this the cylinder is getting too hot. Which cylinder did it come out of?

Re: BIZARRE Spark Plug Color?
 

Looks like high speed glazing. Happens when cylinder temperature increases rapidly under heavy acceleration. Causes the deposits to melt and form a hard coating. What heat range are your current plugs?

Re: BIZARRE Spark Plug Color?
 

Not good looks like that cyl is running lean.

Re: BIZARRE Spark Plug Color?
 

Number 8 cylinder. I don't have a thermostat in it but the 454 never get hot even here in Phoenix.

Re: BIZARRE Spark Plug Color?
 

Not sure, they are just basic cheap plugs from Autozone.

Re: BIZARRE Spark Plug Color?
 

I know you said it doesn't get hot but I would certainly put a t-stat in it and 50/50 coolant mix. The main function of the t-stat is to slow the coolant flow down enough to allow the proper amount of heat transfer from the block to the coolant as well as keep it at the calibrated temp. Straight water has a lower boiling point than 50/50 mix. Straight coolant or straight water can cause overheating.

As for the plug, I would say that cylinder is running hot/lean just as others have mentioned.

Re: BIZARRE Spark Plug Color?
 

I put a T-stat in it but it reached operating temp way fast and was slowly getting hotter so I pulled it out. I'll pick up another one maybe it was bad. I'm confused, how can one cylinder run leaner than the other 7 when it has a carburetor (Edelbrock 1407)?

Re: BIZARRE Spark Plug Color?
 

Intake gasket leak.

Re: BIZARRE Spark Plug Color?
 

No joke, I've been thinking about putting a aluminum intake on it, now just may be the time to do it!

Re: BIZARRE Spark Plug Color?
 

Well if you put that new intake on put a timing light on it an make sure she's time to 12deg or so. Timing could be off but you never know? Even if it is on one cylinder its doing this on.

Re: BIZARRE Spark Plug Color?
 

Do your self a HUGE favor and do a compression test and a leak down test if you have low compression .It is an awesome test that should be done but seldom is!It tells you so much about the condition of your motor.

Re: BIZARRE Spark Plug Color?
 

I'd second that. Spray a little brake clean or carb clean around that intake runner while she's running. Any change in the idle will tell you there is a leak....

Re: BIZARRE Spark Plug Color?
 

I've done a compression test and all 8 are around 110psi + / - 5psi, That sounds a little low to me but what is a stock mid 70's 454 compression supposed to be, 100psi, 120psi, 140psi, 160psi? I've looked online and get various numbers.

Re: BIZARRE Spark Plug Color?
 

I've tried that too and didn't find any changes in the idle.

Re: BIZARRE Spark Plug Color?
 

^^^^^^^^^^^^^^^^^^^^^^^^^this^^^^^^^^^^^^^^^^^^^

Re: BIZARRE Spark Plug Color?
 

That is a little low should be around 140+ try a set of autolite plugs and i would check that cyl periodically.I've had awesome luck with autolite plugs burning clean have used thousands in bikes i've dyno tuned over the years .If you are not loosing coolant or getting it in your oil run it but i would consider rebuilding it some day.

Re: BIZARRE Spark Plug Color?
 

That is bad. You have a problem here and the thermostat is not causing it.

You must run coolant/water mix. Coolant has anti corrosion components, wetting agents, lubricating qualities, and changes the boiling point of water.

A common misconception about the thermostat is that it controls how *hot* the engine gets. This is not true. The thermostat controls how *cool* the motor *could* be in ideal operating conditions. Mechanical problems will make it run hotter than the thermostat can control. Specifically a bad head or gasket will create an air pocket behind the thermostat that will not transfer heat from the coolant to the pellet so it opens to allow coolant to flow.

I would suggest a leakdown test on the cylinder in question. My expectation is you will see/hear air leaking into the cooling system. Bad head or gasket. This would explain the overtemp problem and the plug condition.

An interesting note is that not running a coolant/water mix can cause corrosion and fluctuating temps (excessive expansion and contraction) that can cause heads and gaskets to fail (among other things, burned valves). Not running a thermostat can also cause wild fluctuating temps resulting in the same. So which came first, the chicken or the egg?

Re: BIZARRE Spark Plug Color?
 

How do I perform a leak down test on a budget?

Re: BIZARRE Spark Plug Color?
 

Yea i suggested a leak down and comp test a few posts back sounds like he doesn't have the equipment .