here is a comparison of a solid brass 5-6 lb (weight wise) water pressure pop off valve compared to a solid plastic less than 1 lb (weight wise) pop off valve. I have found that when running a high flow thermostat or any thermostat,the water pressure can get out of hand and in order to keep good low speed water flow and pressure, i made this plastic valve to dump the high water pressure when needed. I made this to save 5 lbs of weight, since i am drag racing my inboard outboard and looking to save any weight i can. It took 7 1/2 hours to machine this plastic piece. I will make some if anyone wants one. thanks