Sorry for late reply to this thread. There is a lot of confusion in the Honda community about the water flow.
I could not get a definitive answer, until, now! Since, I used an electric pump and sold the original and did not
notice the notation in the RSX manual, I have been doubting myself all this time! Thank You!
I did the water flow the right way. Block-first design is most common in stock engines. It decreases thermal stress on the
aluminum heads during start-up and idle. Hence, I made the right choice based on this logic. Also, looking at the
diagram in the RSX manual, the top radiator hose is always for hot water i.e. return from engine. AS the water cools it drops in the radiator top the
Race engines are pre-heated or warmed up carefully. It is more advantageous to plumb the head first, since it is the hottest part
and more sensitive to heat. If you look at all the NASCAR engines (especially when they were based on stock blocks), not only did the water enter the heads, first,
but an attempt was made to have an inlet by each cylinder ot at least front and back (4 inlets).
I would plumb any oil/water cooler (heat exchanger) on the hot side i.e. after the engine and before the radiator. You want oil at 80 to 100C. Oil/Water
cooler warms up the oil when you start the motor (this is good, unless you have a dry sump with a tank heater). The oil flow and lower heat capacity of oil will
not affect the cooling system and vise-versa. We can start a big argument about what the optimum water temperature is, let us not. But
there should be no argument that oil should be between 80 and 100C. Synthetic can run up to 140 and mineral oil 120, but I would not feel comfortable,
if the steady state oil temperature is over 120 or below 70. The ASTM oil viscosity test is conducted at 80 and 100, VI is calculated from that. There is
a separate test for the cold/winter rating. (I still remember doing this with a glass manometer and a stopwatch, 33 years, ago!).
Has anybody tried or knows about running a Honda K motor for track use with the flow of water reversed i.e. head-first with some benefit? (I have no heater, thermostat or oil/water cooler, so I can switch with ease, if it is advantageous. Just remembered that my turbo is water cooled...)
Late to this thread. Coolant flows out of the cylinder head, through the radiator and back into the thermostat housing. I'm 100% sure of this.
When the thermostat is closed the coolant will bypass the radiator via the smaller diameter hose which runs from the cylinder head outlet to the thermostat housing.
I plumbed in a laminova on the radiator return hose, but that was a race car and I wanted the oil to stay around 210F - 230F (which it did).