Hi  Paul,
Was looking at the engine in the attached pic, and sorry to  digress from
the oil line discussion.  I noticed the plug bosses still  in place and was
very interested to find out your preferred plug for  aircraft use.  I
realize
the engine shown still may be in road trim,  being readied for aviation use.
During an engine build I would remove the  bosses for the client so they
could use much cheaper plug options, a big  saving at tune up time.


As well as standard I have tried many other  expensive options and generally
been unhappy with durability.  When I  first started racing $25 NGK B8-10
EGV's were the order of the day.   Not sure what they charge for those
nowadays.  For expensive race  plugs they never lasted long, even with a
points and condenser style  ignition system.  The CD ignition setups I saw
used to chew up  plugs.  Especially without resister type leads.

The standard plug,  surface discharge type, I found less than durable, and
never saw the point  of a plug that couldn't have the gap adjusted.  To be
fair they  weren't designed for high boost or race applications.  And  that
Surface Discharge configuration fits the Rotary well, pointing its  spark
directly towards the combustion chamber.


By the way, I  have no financial interests in NGK. Over the years had very
pleasing  results with a cheap plug used in earlier Mitsubishi turbo cars.
At around  $7, its the B7-8 ES.  The number that denotes the heat range of
the  plug will of course be personal choice and governed by engine and
usage.
They lived with anything Ive thrown at theme, one set did me two  years of
road and race use, I just used to keep them  gapped.

Sammy

http://www.rotaryeng.net/Spark-plugs/Spark-plugs.html

Paul Lamar

In NGK for racing, the 11.5 heat range is used. That is the $25.00  job.
Fine wire center electrode and I gap mine at .010" but they run fine  at
.015" as well.

Anything that has a medium or retracted tip and the same body length will
work fine and crosses to an NGK 10 heat range or colder. In NGK plugs, the
higher the number, the colder the plug.

I cut off the eyebrows as the first move. Then you can use any brand of
plug, rather than just long body NGKs.

Lynn E. Hanover