My order just came in today and one thing i ordered was electric fan thermostat from Perma-Cool(part # 19001) Anyway it has the bulb type thermostat and i can only get it to work when i hold it against the flange between the header tubes. It says in the instructions not to mount it there but its the only place i can get it to work. It is a 170* thermostat and my engine ran up to almost 200 and still wouldn't come on unless it was against the header flange. I tried holding it against the heads the block thermostat housing,heater hose, upper rad hose lower rad hose. Any suggestions? Would it hurt to mount it to the header flange or mount it in one of the rad hoses?

I got myself one of those pollution type thermostat housings with the two threaded holes on top and mounted in one of the holes. Worked fine.

so would it be ok to let it run through the upper radiator hose? So water actually passes around it?

This is the kind i have

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The closer to the top of the motor the more heat. Putting your thermostat switch in the side of the block will get the heat signal halfway up. The motor will be hotter at the top. Thats where you want to get your signal from. If not the thermostat housing,. Then use the spare hole on the intake. I couldn't use this spot because I had a 45 deg thermo spout and there was not enough clearance between the rad hose and the intake.