Hans, there is no need for probe calibration. Assuming your baffling is good then I ask what is your fuel flow at max power (sea level) on take off ? It should be around 66L/ hr. If not then the jet size in the carby needs to be bigger, a ?shop? can do a flow test & do any jet reaming as required.
HTH
Hans, if you just need to see the CHTs indicate thru your 180 then remove the prob and place it in a container of boiling water and see if it indicates 212 F . Cooking Oil if you want to go higher.