Bernie, one thing to be aware of when using other than stock plugs.  The
stock plug has an E designation meaning the threaded portion is 3/4" long.
There are of course many types of spark plugs in this category - however,
Paul Yaw did an extensive bit of experimenting with different types of plugs
for the rotary and discovered that some of the 3/4" plugs that had
"unshrouded" electrodes could be screwed into the lead sparkplug hole
sufficiently far to cause the grounding (outside) electrode to extend into
the combustion chamber and actually clip the apex seal causing damage.  He
ended up pounding some of the "extended" electrodes flat in order to prevent
this from happening.

Not saying don't use unshrouded plugs - but, just thought I would pass this
along.  Here is a link to Paul Yaw's article on Sparkplugs including the
removal of the "Grounding"strap on some types.
http://www.rhinoracing.com/yaw/ignition.htm  Other interesting information
on spark plugs as well.

Ed Anderson


----- Original Message -----
From: <jbker@juno.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, November 29, 2004 6:02 AM
Subject: [FlyRotary] Re: Oil leak at filter solved (unshrouded plug ?)


>
> Al,
>
> What are the make and number of the unshrouded plugs??
>
> TIA,
> Bernie
>
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