The International Cessna 170 Association

Wondering if having the thermocouple ring that goes around the spark plug PLUS a regular spark plug gasket (I know this isn't recommended!) would affect the correct cyl head temp gauge reading?

Months ago during my annual it was suggested I add the spark plug gasket in addition to the cyl head thermocouple ring. Later on a 3rd or 4th flight I noticed the cyl head gauge not working. I removed the spark plug, examined the "ring" and reinstalled it along with the sparkplug gasket. Since that time the gauge has always indicated temps at or below 300 degrees. Previously the temps would go up to 400 in a climb, then back off to around 375. I'm thinking its time for a new thermocouple, but was curious what others might advise.

Frank
The tip of the spark plug needs to be in the correct position inside the combustion chamber. One gasket places the tip in the correct spot. Two gaskets moves it, to what degree it affects the CHT, I don't know but I would only use one gasket, either the CHT or a standard spark plug gasket. I have never heard of using another gasket with the CHT probe.

A spark plug dissipates it’s heat thru the cyl head via that gasket.
The extra gasket would change the affect of the spark plug heat-range design is my thought. Why would you do this...and what basis of approval exists for that?