using car radiators...why not?

[Maglin]

if you are so intent on using a car radiator you should try to source one from an older vehicle as they would more than likely be made of copper/brass, newer rads will all be made of ALU/plastic

I was just about to say this. But the downside is that it will probably already be leaking. The end tanks are usually crimped on with a gasket between the core and end tank.

As for the fins/inch I wouldn't worry about it. The radiator is so hough that thermal transfer issues will be very moot. You can put everything thing in your rig under one loop and still not do much to the radiator. People used to use heater cores back in the early days of W/Cing. It's funny how people are starting to go back to the automotive solutions. But they are way to big and require to much work. Don't forget you have to do something about the filler neck on the radiator. You can't just use a radiator cap on it with a very large pump you are thinking about. I would imagine that internal pressures will rise above 16 PSI or 1.1 bar which will be about the highest pressure cap you will be able to find for a radiator.

And as for cars colling systems using mixed metals and it not doing damage. That is totally wrong. It's not maintaining your car that does damage. Coolant has a lifespan and if not replaced becomes acidic and starts eating away at the aluminum components in the system. It's also a main reason for cars to develop coolant leaks. That and GM designers that can't design a V-6 that doesn't leak coolant.