Heres how mine is done . I have a gate valve at the pump and at an idle the motor wont go over 180 which I think is kind of high but not terminal so I really dont care . When I jump on the gas it goes down to about 140 -150 and my theory is that the water pressure is turned down (I dont know how much because I dont have a gage) enough by the valve to not let the motor over heat but at speed cool the engine enough to still make enough heat for good performance . Another plus is that with the pressure turned down , the pump wont blow out any gaskets . Now tell me how many times do you here of people complaining about how they got milkshake in there motor and it turns out its a blown gasket.

-beerjet-

I think that's what I recomended at first as well. Turn the valve down so there ain't as uch water going in thereby relieving the pressure.     That's how they built them when they were new.   

If you control off the gate isn't there the same pressure, just reduced volume?  If you have 50# in 1/2", you would still have the same 50# but going through 1/4" (or whatever size) so same pressure but lower volume.  You would run cooler at higher rpm vs. idle because the increased pressure will move more volume through the block until the pressure is maxed, then you get mikshake.  I'm going to run a pressure relief for safe keeping and also hoping to get more heat to the block...