Jackson my man!!
The suggested plug (and heat range) is
for "normal" driving which is pretty much
defined as 50% highway, 50% town and
assumes you are not driving around
constantly at WOT and 6,000 rpm's.
It is for the "average driver". It will stay
"clean" by reaching and staying in the
heat range wherein deposits are mostly
burned off in the combustion process and
in normal use will not get hot enough to
approach un-necessarily the "ping" or
"detonation monster" using the recommended octane gasoline in the
STOCK motor.
Now we enter into this "normal and average" equation, your basic
spridget
"lister", most of whom are less than
average and very strange and weird,
except for me (and maybe you, and I
am not at all sure about you at this
point!). <vbg>
OK, let's get SERIOUS here. A lot of
listers are "into" their cars and "tune"
their motors for more power than stock.
They upgrade to larger carbs, increase
compression ratios, upgrade cams in terms of greater lift and longer
duration, mount headers and free flow exhausts,
etc., etc., etc.
More "power", whether in the form of
higher manifold pressures and/or greater
rpm's produces more combustion heat.
This normally calls for a cooler plug.
which transfers combustion heat to the
cooling system at a faster pace, thereby
running "colder" in a "hotter" combustion
process than "stock".
Thus, most listers go from a BPR6 to a
7, as they find 8 to be too cold for even
a well tuned street motor, though this
heat range would probably be very satisfactory were their machines
driven
under race track circumstances, or
supercharged street driven units.
In practice, I have only found 8's to be
suitable for my Judson supercharged
applications in summer weather when
induction temps are on the high side
relative to ambient winter temps, cold
air induction system notwithstanding.
There are also various "tip" arrangements
for the projected nose series normally
recommended and used in Series A
street motors. There are plantinum tips,
iridium tips, splt center electrodes (BPEV
series), "massive" electrode 4 prong
types, etc. It's gotten to be a candy store
sort of deal!! The projected nose series
runs a broader heat range than most
of the other types. This allows for a cooler
plug whose who's "nose" remains clean
of deposits as it is "projected" well into the heat of the combustion
process.
Go down to your local auto parts store
and ask to see their NGK and/or Bosch
catalog and really READ it to educate yourself in these matters.
Bring your favorite drink along and find yourself a nook to sit in so
you may relax
and enjoy while you "learn"!! :)
Cap'n. Bob
'60 :{)
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