internal engine thermostat working properly?

[Chris 1980 SC]

Hello,
I am in the process of diagnosing my 1980 sc's engine cooling problems. Is it safe to assume that the internal oil thermostat is working properly if the oil cooler (in front of right valve cover) gets as hot as the rest of the engine during normal operation. I figure that the thermostat is indeed working, but is there any way to tell if it is opening fully without removing it from the car?
Thanks for any advice
Chris

[quattrorunner]

I went through the same issue in the 79sc. In the end, in an effort to help save you some time, might I suggest just getting a new cooler in the fender that can better support the cooling of our air cooled engins? I tried lots of things and finally got a stock carrara cooler and fan and all my issues were solved. I live in Vegas and my issue may have been more pronounced. Also of no importance to most, the ruf front bumper with holes for fogs left open my cooling was even more easy to regulate. Good luck.