How to read Spark Plugs - detailed info

Reading the Source info, these information are from 1977, so no unleaded fuel covered I'd say, right? Be careful using the information if you use unleaded fuel...
 
its an American magazine article
and unleaded was common from about 1965 and almost universal from about 1970, or so I was led to believe when I was very interested in Jaguar cars, and have heard it said many times since then, that unleaded fuel is very difficult to read on a spark plug as a conventional plug chop.
CLEM
who blew holes in two pistons, with land damage to the third last may
 
Gordon Jennings (RIP) was tuning with un-leaded fuel..being in the peoples republic of california. He wrote this because people were still looking for lead additive deposits when reading spark plugs. The problem was racers were adding advance and running very rich mixtures to get the old look on the plugs. Too much ignition advance and a rich mixture ( he states only a very, very rich mixture would suppress detonation ) would hole a piston in short order.

His prescription..less advance and a leaner mixture..look for the mixture "ring" inside the insulator and the electrode tip of the plugs for too much advance. Good advice with modern fuels
 
Frigging easy to read spark plugs don't know why people have so much trouble!!

Just look on the porcelain for the little letters and numbers and hey presto!!!  BP7ES!  BPR6HS  etc, etc.
fucking ejits!

Julian
 
Well I suppose reading spark plugs might be a useful skill, like interpreting tea leaves in a cup, Gypsy Rose. But not much of a substitute for some quality dyno time with someone who knows what they are doing...
 
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If you really want to read your spark plugs, do get a tool for the job. This spark plug magnifier is from Champion in the 70's. It reads NGK spark plugs too :LOL:. Always easy to look for signs of detonation, mixture and spark plug heat range.

A good spark plug magnifier will save a lot of pistons.

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Paul LeClair said:
Here is a link to a great article about How to read Spark Plugs, by Gordon Jennings. Highly recomended.

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

Paul LeClair
Click to expand...

Thanks for posting that Paul, a great article by a great guy. I remember using this information when I was first starting out building and tuning, with unleaded fuel. Then once I was wrenching at the track it was amazing how much easier it was with leaded race fuel. You can read plugs with unleaded, the signs are just easier to read with lead.
 
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