ok I just bought a heater core for $25. I noticed a 4c drop in my temperature. Another thing I did was remove the waterblock for the chipset cooler. The fact that my cpu was running over 45c made the chipset run hot. It looks like I might buy a blue orb, and install.
Those bloody Blorbs add more noise than Pump, drives and 8 slow fans combined in a water cooled systems. Try some other solutions first. Stock chipset sink with a 486 fan snipped out of it's housing and epoxied to chipset sink is what I'm using for now. I'm sure there are better ideas. Just would not recommend the Blorb when watercooling.
I have a transmission cooler in my system right now but I have a heater core out of a Toyota that I am going to try after I get back off a job in Houston I have to go on today. The heater core should do a beter job because it will hold the water in it longer to be cooled. As far as alum. verses copper and corrosion goes. If you use an antifreese with your water it has anticorrosion cemical in it. If you don't want to use antifreeze you can get a bottle of electolis cemical from a truck parts house. In a big rig you have such a large volum of water that you have to use that to keep from eating holes in the cylinder walls. It will not take very much in your system. And if you change your water every once in a while you won't have any problems.