Plug Cuts

[bruce plecan]

A plug cut allows you to see what is going on in a combustion
chamber.  But, you have to know what you're looking for...
And that's the hard part.  Over the years there has been much
written about plug reading, and all kinds of charts.  If ya can
get some of the old Circle Track+Racing Technology Mags
several years ago Smokey Yunick did a 2 part series, and 
the info was accurate, from time to time Champion has
really nice charts showing plugs, that are easy to read, and
in the Dr's Book to Optimizing Your Ingition Book has a 
chapter on it.  IMHO all of these sources seem to be accurate
and true.
  Items needed for doing plug cuts, large open empty road,
spark plug wrench, magnifing glass, some spare new plugs,
  Rule 1.  To be any good you have to do the road part in
               a tranny gear of 1:1..  You want to load the engine
               down, and ya can't do that when you have any
               mechanical gear multiplication (ignoring the final
               drive)
  Rule 2.  You have to maintain this load long enough to 
               color the plug (seems to vary with engine type
               and level of tune).
  Rule 3.  Do as many as you can in one test, to minimize
               atmospheric changes.  (BTW some racing teams
               are checking O2 levels in addition to atmospher).
  Rule 4.  Beleive what ya see..  Don't dimiss the obvious,
               or ignore a problem.
  Rule 5.  When doing testing gather as much info as 
               possible as far as the car, and atmospheric
              conditions.  IE I use a Air Density Guage,
               Temp, and Humidity.  KEEP A NOTEBOOK
               AFTER DOING THIS SEVERAL TIMES
              you might begin repeating ground you've
              already covered, and just waste time.
  Rule 6.  KEEP A NOTEBOOK

The easiest plugs I've found to soot are champion.
If you have any pinkishness in the coloring get a
  different brand of gas (Shell used to be really bad
  for this).
The longest lasting street plug seems to be autolite
  (the center electrode has min erosion)
If changing brands of plugs makes any difference
  you have an ignition problem.  All your expensive
  plugs are just crutches for a poor ignition system
  (again IMHO).
Some engines like certian brands of plugs, again
  IMHO
  GM like AC/Autolite
  German/Italian Champion
  Japenese NGK/some autolite champion
  Ford Autolite/AC
  Dodge I forgot think was champion
Yes there is more but that's for later
HTH  Bruce    Again from the 97 FBI DOJ reports
                      there seems to be no dangerous
                      gangs wearing cone shaped hats
                      (they also specify danger as to 
                      mean to the general public).....