Colder air is more dense than hot air. As such, the same needle settings will lean out the engine as temp drops.

Cold air requires more fuel to keep the mixture right...
More fuel means more lube and lower temps...

Corse-R is on the money. Below 20-25 deg ambient temp dont try and chace the same engine temps you run at 30+ deg.

corvette... google "conversion" you will have you answer alot sooner!