OK, there still seems to be some confusion over the direction of water flow, so one more time.
1.
The water flow is from the bottom radiator hose thru the center of the water pump thru the engine block, up thru the heads from rear to front and then back out to the upper radiator hose.
Note: I am making some assumptions based on my idea of how this modification is supposed to work, since I have not actually seen pictures of a completed one.You have never given me a link to a site that shows one installed
Note: I can see two possible ways to hook this arrangement up.
1. The way I mentioned before by putting the Y in the return hose from the heater (the one that is attached on the engine side of the Tstat), this will draw (pull) water from the Tap. I would expect this to put water back to the radiator that hasn't been heated by passing thru the heads and reducing the temperature of the water comming out the bottom of the radiator.
OR
2. If you want to introduce (push) water, that has NOT been heated by going thru the engine block, to your tap, then you need to reverse my previous usage of the Y. In other words put the Y in the hose that that supplies the water to the heater (the one that attaches to the water pump)(bottom of the Y toward the water pump). This is from the pressure side of the water pump.
Of the two possible arrangements I see number 2 as the least possible cause of problems such as robbing the heads of sufficient water flow. Also, I don't see any real advantage to this over installing a Heavy Duty radiator and possibly a Transmission AND/OR an Oil cooler.
Hope that helps!
Good luck,

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