Dallas-
What does your engine builder say about the
oil temp?
If you haven't confirmed that the
oil cooler is plumbed properly, then that would be worth checking. If you elect to check the accuracy of your gauge, handle it with care. The small metal tube that goes from the sensor to the back of the housing in the dash is rather delicate, so avoid sharp bends or kinks. It contains the working fluid (ether) and a small hole will cause the thing to fail. You should be able to set up some kind of portable heat source so you only have to remove the sensor from the
oil filter adapter, and dunk it into the water bath. Be sure the sensor doesn't touch the sides or bottom of the boiling water container.
Good luck.