How to Diagnose engine from old spark plugs?

[spriro]

Here is a pict of my plugs after 103400 miles.
Does it look normal?

[lee polowczuk]

looks superb...

You need pictures looking down into the business end of the plug. The pictures posted are not much use for this purpose.

The single plug looks as if it is bridged. Need better pictures.

You can look in most any repair manual and find a chart or collection of pictures that show you what to watch for.

Merry Christmas,

[kramlavud]

Larry,

I think the 'bridging' you see is a shadow of the negative electrode on the surface behind the plug. Look at the similar shadow along the right side of the threads.

I do agree with your request for a better pic, and advice to check any repair manual. Alos I bet there are pics on the net of spark plug problems.

Mark

[Jackd]

Have a look at http://images.google.ca/imgres?imgurl=http://www.dansmc.com/spcarbon.jpg&imgrefurl=http://www.dansmc.com/sparkplugs1.htm&h=471&w=578&sz=48&tbnid=tfM0suOlWN4J:&tbnh=107&tbnw=131&start=105&prev=/images%3Fq%3Dspark%2Bplug%26start%3D100%26hl%3Den%26lr%3D%26c2coff%3D1%26safe%3Doff%26sa%3DN and compare your plugs to the various pics and see how they compare.

[Ron in SC]

I copied what appears below. The person who wrote this is very experienced with Porsche cars.

To "read" spark plugs, one must perform a proper plug cut, that is; switching off the engine after being held at a specified RPM & throttle position for 10 seconds or more.

Keep in mind that unleaded fuels read differently than the old leaded ones and a normal center insulator colors up (under load) a very light tan, reddish brown, or almost white, depending on the brand of gasoline. One big thing about reading plugs is observing the positon of the fire ring on the insulator. This tells the reader how hot peak combustion temps are.

It takes a fair bit of experience to accurately read and interpret spark plugs, but its quite accurate when you know what you are looking at....

[spriro]

Thank you for the replies.
I'll see if I can get a better pics later.

[spriro]

A better image to evaluate?

[manny]

Far as I can tell, the plugs look very good, considering they've got 100 k miles on them.
Personally I would not run plugs that long, mostly out of fear of ruining a thread on removal.