Paul and group,

I have Tracy's EM2 installed in my Bush Caddy, and need to install
two CHT thermocouples. I purchased two under the plug thermocouples,
but don't have enough room for the thermocouples to clear the spark
plug and the rotor casting.  Does anyone know how much rotor
material is around the trailing plug  in the area just under the
plug?  My thought is to grind out a small portion of material, 3/16"
wide at a 45 deg. angle with a die grinder just under the plug to
give me enough clearance for the thermocouple wires.   I have
attached photo's to illustrate what I would like to do.  The photo
(0164) with the black marker is where I would like to remove a
little material.  I'm worried about grinding into the water jacket.

I have seen the photo's of the drilled hole in the rotor for
placement of a thermocouple some people have done, but that looks
like it is something that needs to be done with the rotor in a drill
press, and not free hand.  My engine is installed in my aircraft.
Thanks for any advice and comments.

Bob Forbes

Upstate NY

N164WF

There is quite a bit of material there so a bit of die grinding
should not hurt. The internal fins are not necessary in case you
were wondering :)

Paul Lamar



I would think it would be better to install under the leading plugs as the
heat is higher there. It would give a better and quicker temp reading. Temp
readings do not change quickly in the metal on the outside of the housing,
but
reading at the trailing plug will give an extra delay.

Dale Davies


Paul,

How much good will the TC under the plug actually do as there is a water
jacket between the combustion chamber and the outer housing surface.  Seems
that you will only be reading the coolant temp, not the actual CHT.  Someone
needs to come up with a dril jig so that the 1/8" TC hole can be safely
drilled without having to disassemble the engine.

Mark S.

Not much. Better than nothing :)

The drill jig would be easy to make as it can bolt to
the lower (Leading) spark plug hole. Good idea Mark.

Paul Lamar