Electric Water Pump Regulation

From what I can tell the Melling "Temperature Control Valve" is merely an electronic thermostat. You get more precise control because the computer can determine when to open or close it, and there is no ramp-up -- it appears to be all the way open or all the way closed (the square form of the graph). That won't really give better temp control at all. It will allow a faster warm-up, which will reduce emissions a bit.

More interesting is the clutch water pump. An electric clutch to turn the pump off and on by computer. Shouldn't be too hard to make an adapter plate if a suitable size and shape pump can be found, convert to an old engine!

In both cases, what makes them work well for precise temperature control is the COMPUTER SOFTWARE -- or computer control. That's the point TomJ is making. To get precise control you have to have  precise controller. If you're not going to do that you can make some improvement to the old system, but not much. There is a reason no one uses an electric pump on street cars!

Main reason is reliability. A water pump motor should have more load and draw more power than a fan motor, and it will cycle on and off a lot more. The fan cycles off most of the time during cruising when there is a lot of air flow through the radiator. A pump motor would constantly cycle on and off. Might be short on time due to more air flow, but after a minute or two with NO water circulation at all it would have to cycle on for 30 seconds or so to cool the motor back down. Something like a 120 second off/45 second on cycle even while cruising... maybe more (less time off and on, faster cycling) in city traffic. That is a lot of relay cycling!

With computer control I'd go with the pump like TomJ did instead of an electric t-stat (temp control valve). You would get a little convection flow through the radiator and engine all the time (the early Renaults with the radiator in back and little hood used convection for all flow -- no pump!), and the pump can be variable speed.

for an analogy on how/why the complexity of the electronic system is, vs. the simple old pump and thermostat, consider how basically simple a carburetor is -- and how insanely complex good EFI is. it took 20 years, or more, for EFI to be really usable. there's a lot of subtlety and complexity hidden in that chunk of metal.

Have a look at these:

You could just drill an AMC t-stat, of course. If you're constantly running the pump you may as well leave the belt on it. There is a bit of efficiency loss running the electric motor from the alternator. Better to run the pump directly if it's going to be constantly on. There is some temp swing even in a stock system -- as much as 20-30 degrees in some cases. I can see my temp gauge drop 10 degrees when the t-stat opens. The sensors and gauges aren't particularly fast either. It won't hurt to have a 20-30 degree swing in temp. You gain a little power and mileage from an electric fan because it's not pulling all the time, not because it's electric. A clutch fan gives you back a little as well, though you're still turning the mass of the clutch and fan hub, so not as efficient as an electric fan. If the electric fan was constantly on, there would be little to no gain, as the alternator is working harder and dragging just about as much as the fan would.