Cooler engine temps reduce KR and promote cooler intake air temps. Our high flow thermostats feature openings 20% larger than stock for increased flow.
A non-drilled 180 stat is recommended for the 2004+ GPs, 2000+ Bonnevilles, Monte Carlos, Impalas and Regals or an engine code can be set. If you want to run a drilled or a 160 degree thermostat you may need to run our ZZP PCM because we have the ability to delete the 0128 code and to avoid a rich condition because the coolant temps are so low. The drilled thermostat will cause the engine to take longer to warm up, this is only beneficial in a situation when your car is sitting, not running, and is started up to race before the engine gets to temperature. For example, when in the staging lanes at the race track. Plus it flows a little bit of water even when the car is not to running temperature. The thermostat is still closed, so it frees up the parasitic loss of the water pump turning without the ability to move water. Since a drilled thermostat will take longer for your engine to warm up. Your gas mileage will also be reduced.

A 180 is the coldest generally recommended for the N/A 3800. Thermostat housing bolts: 21 ft/lbs.

Does not fit the LS4 v8.