I'm willing to take @GW8IZR's observations at face value, In my experience Rover V8 engines can be very sensitive to coolant setup's and more flow isn't always better. I've had a few Rover V8 cars over the years, my landy running on LPG was a pain because the evaporator is plumbed into the coolant circuit, but trying to get it balanced with the heater matrix and the radiator was fun. You either had a working heater but had to be careful not to overheat when sat in traffic or a duff heater and the radiator cooled the engine okay.I've proven that the delta between the rad inlet and outlet was less when the stat was missing, the flow was greater - that was enough for me.
I've no desire to argue.