Are you talking about on the highway or on a dyno? On the highway you are moving so air is moving over the radiator and removing heat. MUCH more air then the fan can move. We have talked about missing air dam under the front end alone can cause over heating.

As your engine runs roughly 1/3 of the fuel energy is turned into heat. How much HP a radiator can handle has 2 major factor, the area of cooling fins and the CFM of the air going past it. If you reduce area of the fins or the CFM you reduce the radiators ability to bleed off heat. If the CFM of air drops to zero so does the radiators ability to handle any HP.

I have similar results as you had with my 1996, she stayed right at 180 degs on the highway or even at 25 MPH. Sitting still in traffic temps climbed until the fan kicked on then they dropped till the fan kick off. On a cold day I can run the heat full blast and it would almost not get hot enough for the fan to kick at idle.

My LS1 temp gage goes right to straight up and down 210 degs and never moves. In fact it moves so little I don't trust it. I am working on a OBD2 tablet that shows real time computer info. The plan is to use it for music and have a split screen for engine infor and a Wifi Back camera.


The above articular does say 220 operating temp is normal so temp is not his emission problem. GM would not build a car that required supper accurate temps in order to pass emissions. You figure these cars are used in Canada, Death Valley, Winter or Summer. I would guess a new car can pass emission at 210 or 240 which GM would say is normal. Remember the high speed or second fan does not even turn on 235 degs.

 

i seen that, mine must stay low cause the temp here never gets that warm, also i question my temp gauge, when its 100 degrees out it still just rises above first mark. i agree the test station is wack to say its running too hot. wonder if the 02 is not heating and the comunication from the test guy is poor.