And after driving it 75 miles or so in the past week I noticed that the car runs at 205 degrees on the temp gauge. I confirmed this with the infrared heat gun (so the gauge is actually accurate!). The temp would never rise above that, even when sitting in traffic or under throttle - very stable, just hotter than I would like.
Since the thermostat housing was leaking I decided to check the thermostat. Looks like it was the original thermostat with a Delco stamp and a 195 rating.
The unique "LS2" ID stamp on the SD455 intake, and the leaky thermostat housing:
"DELCO" on the top side:
"195" rating on the bottom side:
Since I had a spare 160 thermostat on the workbench, I threw that in, replaced the gasket and tightened everything back up. While I was there I used a little Windex and gently cleaned the area surrounding the housing. With the 160 thermostat in it, the car runs much cooler now - like 160 or so - barely hitting the first notch on the gauge on a 75 degree day today.
