It was already like $400, keeps my car plenty cooled, takes like 10-15 minutes of idle to get the fans to kick on, and it solves the problem of plastic capped radiators. ..wouldn't brass be way heavier?

 

10-20% heavier yes, but still far, far better at all the important features. If your worried about heavier = slower then raise your boost a few PSI and get 10-20 more HP out of the motor.

 

Not sure this is for every application. My understanding is for a radiator to be better and be cooper it will weigh so much it's ridiculous. Also with older cars if they come with aluminum switching to copper brass is never considered a good idea where if you're car had one of these to begin with you might consider upgrading to aluminum. Take the older corvettes for example. Anyways I've never heard of anyone considering it an advantage over the aluminum radiators in a turbo subaru, the koyorads are great, don't see why you would add more weight.

 

Another thing to consider if you're using a brass radiator is the fact that not any kind of coolant can be used. There's certain chemicals in the various coolant formulations (like Dexcool) that will damage those radiators.