At 10:34 PM 4/1/98 -0600, you wrote:
>Hopefully this won't lead to the debate the last spark plug question led
>to. What does it mean when a spark plug is hotter or colder? Given
>that I have MSD 6A and Blaster 3 and headers, should I shoot for hotter
>or colder or stock plugs when it comes time to change them?
Well Robert, a hotter plug retains more heat than a colder plug. You want
the plug to run about 750 degrees if I remember right. With the variables
of localized cooling and chamber temperature/pressure you will sometimes
have to vary the plug somewhat. Unless you have really super modified the
motor stock types will probably be just fine.
Here is my way of reading the plugs if it helps:
1) put a stock new set in
2) after 50~100 miles pull a couple of the plugs, and with a loom (handheld
10x microscope with a light) look at the center electrode where it meets
the porcelain. You should see a light blueing of the center electrode
metal if the plug is hot enough. Autolites may not show this well since
they are darkly colored.
4) after a 1000 miles (street truck here) take a small flexible light (in
the automotive section) and position the bulb so that you can see the area
where the porcelain meets the metal casing on the chamber side of the plug,
the porcelain should be lightly tanned only at the base. If this line is
black then the motor is slightly rich (keeping the pedal down will do
this), and the line should be only at the base, not halfway up or something
is either too cold, too rich, or the timing is a little weak.
5) any coloring should be dry appearing or you got problems.
3) with gasoline the plugs should otherwise look like they just came out of
the box. The porcelain will appear a little "drier" than a new one, but
that should be it.
6) most important, take the loom and look at the porcelain carefully, if
there are small spots that look like "fly shit" you have detonation whether
you heard it or not. You never want to see these spots.
Smokey Yunick about 5 years ago wrote an excellent article in Circle Track
about plugs if anyone can find it. I have no clue where my copy is at the
moment.
Hope this helps
Nicholas
Nicholas McKinney
Applied Industrial Technology, Inc.
www.usaait.com
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