<VV> Spark Plug Diagnosis Question

[Mark Durham]

Jeff, we'll have to see who responds, but I think #6 might be the
hottest cylinder of the 6, because it is over the longest exhaust log
and is also back in a corner. Its also the farthest from the
carburetor, like #1 and will run a bit leaner. #5 probably also runs a
bit hotter but not so much that you would notice. Its interesting that
they put the CHT probe at the other end of the engine where it stands
to be cooler, in #1. There are guys out there that have installed 6
cyl chts and could let us know if I am right.

With a engine that has a ducted fan on top, supposedly all cyls get
the same amount of air, and that may be true in theory, but things
like cylinders not being de flashed, or the fact that the engine is
closed off on the bottom and only lets air out when the engine gets to
a certain temp, and that cylinder is the farthest from the outlet, it
stands to reason it is hot.

While looking at the plugs, have you compared them to plug charts off
the internet? If the plug is completely white and has little metallic
globs on the ceramic, that cylinder is close to or at detonation, and
you may want to look at timing, gas quality, etc.

Mark Durham



On Fri, Nov 26, 2010 at 9:17 AM, Jeffrey B. Aronson <jrh at foxislands.net> wrote:
> Hi Experts,
>
> Before Thanksgiving I completed an ignition tuneup by installing new
> spark plugs in the Monza 110/4.
>
> One question:
>
> 5 of the plugs [AC's from Clark's] looked as expected, as they were last
> changed in the late spring - brown with no oil or carbon deposits. #6
> plug looked quite white, as if it ran hot. In September, when replacing
> the flywheel, Ron Tinkham and I noticed that the oil cooler was rather
> clogged up, so we cleaned it out. If that was a cause of hot running,
> I'd assume that all the cylinders might run hot, too.
>
> What might cause the #6 plug to burn white at the tip like that?
>
> This time, I've tried Champion plugs to see if there's much difference
> in daily use.
>
> Thanks in advance,
>
> Jeff Aronson
> Vinalhaven ME 04863
> www.landroverwriter.com
>
> '66 Corvair Monza Coupe 110/4
> '66 Land Rover Series II-A 88" SW
> '80 Triumph TR-7 Spider
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