I've asked a similar question in another topic.

I had a Pro Alloy i/c put on yesterday and the car is running a lot warmer than usuall which i thought might happen as there is no direct air flow to the rad ... but at the same time, my rad might not be upto its real job.

i did a search before posting, and found 80% of the time, people put a 82 degree thermostat and a manual fan switch in place. Also noticed that alloy rad's help keep the engine cooler when sitting in traffic, but theres no real difference when travelling.