Dirk, one thing that might be happening is that your water pump is too good, I tried a new 3200 cfm fan and it did not change a thing, my temp still ran at 220. The pump is pulling the water through the radiator so fast that it doesn't have time to cool. That's what happened to me. I took out my thermostat and replaced it with a restrictor washer, I used the medium ring. Temp now runs between 180 and 190 even in 100+ heat. I have a Backdraft, I got the part from Reg at Backdraft. If you go to the Knotts cobra meet this Saturday 4-25, go to the Backdraft display and talk to Reg, I'll be there Saturday after 9AM also, or you can find him at
www.backdraftracing.com Good luck Steve
