I've now got about 3 hrs since chrome MOH on my J-4 with it's C-85 engine in a pressure cowl arrangement. The cyl temps on the rear two cyls are running about 400 DegF (both under the lower sparkplug thermocouples) and the oil temp is running about 200 DegF at 80 deg air temps. I built new baffling for it based on C-172 practice with emphasis on getting it tight and rigid to the fins to force all air thru the fins. It has an air outlet flange to increase the airflow as well as side vents ala PA-18. Oil is Aeroshell Grade 80, and there is no oil cooler. There are intercylinder baffles and head intercylinder baffles as common to this engine installation. The oil stays very clean and it doesn't seem to use very much at all, suggesting the rings have seated well. The engine seems loose & broken in otherwise.
Do these temps seem out of line? Cruise airspeed is only about 85 mph so the cooling system doesn't really have a lot of pressure to work with. What sort of temps are any of you seeing on your Cubs and Champs etc w this engine? I realize many may not have CHT.