water bypass valve ????

[HotDogz]

I am running with a 4 port thermostat and TT waterjacketed headers and I am questioniong whether or not I really need a bypass valve or does all the extra water pressure go out the header dump? :confused:

[Taylorman]

I think the thermostat has a 15 lbs spring in it. I think it will dump water if it goes over that.