There was a 22" big block b-body rad in my 'Cuda when I started working on it. After sitting for 25 years, when i took the hoses off of it, and the water drained out of it effortlessly. I ran about 5 gallons of luke warm water through it to clean it out(no rust came out of it), and filled it with a 50/50 mix. When I got the car running, I put a 160* thermostat in it, new engine wiring, and a new temperature sending unit and drove it. Within 5 miles, it was close to 230* degrees. I had the rad boiled out, reinstalled it, and the car still did the same thing. The point I'm getting at is that smoothflow through the rad doesn't always mean good cooling ability.
So, I replaced the rad with an aluminum one from Mancini Racing, and a mopar peformance aluminum water pump. In the summer time, the car will not run over 180 degrees, no matter how long I sit and idle. If its 70* or cooler, it hovers from 155-160*. I would upgrade to this rad and water pump. It was the best investment I made. This made all the difference in the world.
The old waterpump was moving coolant fine. The cooling vanes on the pump impeller were still there, and had plenty of surface area to move the water. As others have described I've seen pumps where the impeller vanes where gone, and it just looked like a thin fan blade. The pump was unable to move any water in the engine in this case. All of these pumps I've seen have been ford pumps though.
