Temp Gauge Sending Unit and Aluminum Heads
I have a street 406 small block with aluminum AFR 195 heads and I am having some temp gauge problems. When the truck is idling, the temp gauge moves up into the 220-260 area. When I start driving again, the gauge goes back down. It's clear to me that the engine is not actually overheating and I have verified this with an infrared thermometer at the water neck. At first I thought it was a bad sending unit, so I replaced it. It was old anyway, so I didn't bother testing it. The problem was completely unchanged. I also used the thermometer on the sending unit case and it also shows an increase in temperature when this happens.
The heads do have the steam holes drilled, but I am starting to think that the gauge is just picking up hot spots when the coolant flow is minimal. Does this sound correct? Should I move the sending unit to the intake? Not worry about it?