[THEFERMANATOR]

I ended up replaceing that valve on my V-4. I had re-sealed it several times with no luck, it had a groove cut in it from the years of service. That valve also bypass's the T-stats for high RPM opersation. It puts pressure on the diaphrams to make the T-stats seal off and bring it up to 160 at low RPM's. Like SKOOLS said, around 3000 RPM's the valve diverts the water pressure to allow the cooling water to bypass the T-stats and the engine temps drop. If you had a temp guage you could watch the temp drop when the pressure is diverted. The higher temps help these loopers to idle better and burn the fuel easier.