In article ,
"Kyle Boatright" wrote:

I know of two kinds of CHT thermocouples - the ring type which attach at the
spark plug and the probe type which thread into a fitting on the cylinder.

Conventional wisdom is that the ring type will show significantly higher
temperatures than the probe type. I've seen differences reported as up to
50F between the two types.

Someone has read John Deakin's recent AvWeb column. :-))

Email Deakin and ask him if they have tested the ones from different
manufacturers and ask him which were the most accurate in their test
stand runs.