Spark plug condition opinions

[Daytona]

Just looking for info on the burn condition and what it tells about my engine. This engine has 170,000 miles + and never had a valve job. Car runs very well with minimal oil loss and engine does not smoke. Puff of smoke only after sitting for a week. All six plugs were similar. 1988 3.2 Carerra, all stock.

[Joe Bob]

Not the best angle or pic. But grey means lean. Brown is good.....balck sooty is rich.

[DRACO A5OG]

Never Valve Adjusted Really? How did you manage that?

+1 too lean, how are the other plugs?

[slodave]

Originally Posted by DRACO A5OG

Never Valve Adjusted Really? How did you manage that?

He means that the valve guides have not been replaced, like mine (over 230,000). At least, that's how I read it.

[Flat Six]

Originally Posted by Daytona

Just looking for info on the burn condition and what it tells about my engine. This engine has 170,000 miles + and never had a valve job. Car runs very well with minimal oil loss and engine does not smoke. Puff of smoke only after sitting for a week. All six plugs were similar. 1988 3.2 Carerra, all stock.

Here's a link from Bosch on interpreting spark plug condition:

http://www.boschautoparts.com/Technical%20Resources/Spark%20Plugs/SparkPlugFaces.pdf

Also, when you intend to pull plugs in order to read their condition, remember to run the engine up to operating temp then park and shut off (no idling). That'll help ensure you're reading plugs' running condition (idling can burn off deposits and/or change coloration, giving you a less informative interpretation).

HTH

Dale

[db_cooper]

With our modern fuels..the indicators for rich or lean conditions have changed. The "brown is good, "white is bad" really dose not work anymore. With no lead in the fuel..the marker has changed.

Reading plugs after they have been run for some time is very difficult..even for the experts.

If you remove spark plugs from a modern engine with 5k on them..the insulators will all be clean and white..they should be.

The mixture should be lean enough to only leave a small dark ring at the base of the insulator..down inside the plug. You will need a light and magnifying glass to see it. Champion used to make a tool to do that. Cant tell from the picture.

The porcelain insulator should be very clean and look new. Hard to tell..looks OK from running around and idling, there is a dark fuel mark. Not a problem with old plugs.

The ground electrode should be burning off the fuel deposits almost to the base..as the picture shows..this means the heat range of the plug is very good.

The body of the plug that is exposed to the combustion chamber..will tell you how clean the cylinder head is running and the temperature. It should be very dark..as it is in the picture.

Most tuners will, using the old school, tune the engines with too much advance..too rich a mixture and too cold a plug. Those plugs will look brown.

Gordon Jennings was a master tuner..God Rest his Soul. Here is a reprint you may find helpful.

http://www.strappe.com/plugs.html

[Eagledriver]

That plug looks fine. If they all look the same that means all cylinders are firing and none are burning oil. Even if it is lean (I don't agree with that reading), it won't hurt anything.

-Andy