I'm surprised with 11 replies NO ONE has actually answered as to why running no T-Stat is BAD! The reason remains that the thermostat not only regulates the temperature of the coolant, but also keeps coolant PRESSURE in the motor! Without a restrictor (a small opening), coolant will not be able to reach the higher coolant passages in the heads causing the coolant to flow slowly and weep throughout the motor without cooling critical areas. All this non-sense means hot spots, randomly throughout the motor, which can lean to detonation on certain cylinders.
YES, you can GUT a thermostat (cutting out everything except leaving the hole) and still maintain optimum pressure or even run a 160 thermostat.
I'm currently running a 160 thermostat with 4 drilled holes around the outside and it works GREAT in the summer (highest it ever got was 180) on a stock cooling system. I went from a 195-180-160-160 w/ holes and the only difference I noticed was a COOLER water temp! I also run a GUTTED thermostat on my 85' and the motor cools A LOT better than when I tried the 160-180-195...Despite a lot of people saying running cooler than 160 degree's is bad for your motor and what not, I've never had a problem. Go with a 160 or 180 thermostat!!
BTW- All my info has come from many cooling experts including Stewart Water Pumps and Griffin Radiators and my EXPERIENCE! I hope I helped