Thread: Spark plug question
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  #8  
Old 05-30-2001, 06:38 PM
Arthur Dalton Arthur Dalton is offline
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,804
I think "o" is for high heat plug insulator.
They are used on engines like the 104 where the plug is recessed in the head and covered.
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