Thanks John, I aklso assume the smaller i.d. would help proportion the water flow rates, which is why I said may
need a restrictor.
onovakind67, I do understand that the water at the rear water port has already been through the cylinder head in order to get to the water port, but that would that water have only passed though only a very small portion of the cylinder head?
Are we to assume/hope that the water leaving the rear port is water that has cooled the two rear cylinders on each bank? ..or perhaps, much more or much less?
The suggested restrictor is simply to ensure the flow rates are what we hope they are.
The restrictor size that I suggeted (5/8" dia) was a detirmined size from a guy down here (John Bennet) that did a lot of R&D on cooling systems. He has a water pump dyno that he flow and pressure balances water pumps with, and he had his own brass impellers made for him that he'd install with a tight clearance long before Edekbrock were doing that with their Victors, and probably before Stewart were as well. In fact, I still have my cast iron BB pump that he modified for me. Worked very well in my application.
In the 80's. he also made a set up where he fitted the thermostat in the lower radiator hose to control the water temp before it entered the block -so cold water from the radiator wouldn't "chill" the front two cylinders. Now all the OEs seem to have the thermostat on the inlet side of the cooling system.
Last I sopke to him, he was manufacturing and suppling parts directly to Ford Australia. He's a smart cookie!
I used to run the 4 corner cooling too. Admittedly, I never had any cooling issues, but that's not to say that I would have with the regular OE set up. I used the restrictor size that I suggested.
I also agree with much of what you have said about the coolant flow. I am not disagreeing with that, I just hope it does what we assume (?) it does..