The dyno system I had at one of the public school auto shops I ran had a water-to-water heat exchanger instead of a radiator. I'm thinking about building my own system like that, using a 55 gallon ring top oil drum and a series of copper tubing coils. The engine coolant will circulate with the engine water pump, and the drum will be filled with water. If I want to run a specific engine temperature, the drum can be equipped with a thermostat, and refilled by a toilet tank float valve. The cooling system coils will have a radiator pressure cap, just for a safety release if necessary.
Jerry
