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reading sparque plugz

To: mgs@autox.team.net
Subject: reading sparque plugz
From: wzehring@cmb.biosci.wayne.edu (Will Zehring)
Date: Tue, 17 Oct 1995 08:55:40 +0500
Fellow fiends:

I have a few questions on the art of reading spark plugs.  The pix in the 
haynes manuals and my own limited experience are about all I have to go on 
for this and I'd like a second opinion on a few general questions and on the 
specifics w/ my B.

question one:  It is my understanding that checking the plugs for clues to 
proper mixture should be done only after the engine is fully warmed up and 
then too only after a run at highway speeds.  I've heard that just idling in 
a parking lot or at a stop light will alter the plugs appearance, making the 
'reading' less informative.  That is, really, for best results one should 
almost go so far as to shut the engine off and coast onto the breakdown 
lane.  Sounds a bit extreeme, but what do I know?  Is any or all of this true?

question two:  Someone somewhere told me that all bets are off on the 
traditional methods of reading plugs with unleaded gas anyway.  Is this true?

now to the specifics on Old Whitesides:  
After a weekend of highway driving and a few miles of surface streets, into 
the garage and engine off:  
        plugs 1 and 2 have a medium brown appearance on the electrode and a 
dry black color on the threaded ring around the electrode (fwiw: #2 is 
slightly darker brown than #1).
        plugs 3 and 4 have a dirty white appearance on the electrode and a 
dry black color on the threaded ring around the electrode.

I haven't check gaps since mid August, when they were fine.  

My interpretation: the rear carb is lean and the forward carb is perfect.  
The dry black color suggests that my oil 'consumption' is attributable to 
the poor seal at the rear main in this early 3-main engine, and not to 
excessive burn.

Comments/suggestions/flames?

Will Zehring


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