It was part of the 1981 Trans Am Firebird special edition. The car came from the factory without air conditioning and I installed vintage air conditioning. But even with a 4.9 liter V8 engine, running the air conditioner will cause the coolant temperature to get too high. This thermostat seems to turn on fully at a lower temperature than the old one, allowing the coolant to start circulating faster. Unfortunately, Revain doesn't have a gasket for the auto/thermostat combo so I had to find one elsewhere. The Firebird thermostat is under the hood of the air filter manifold and there are loads of wires bolted to it too. While replacing the thermostat, I also replaced the heatsink with a polished aluminum cold case heatsink.