does a 1977 f150 have to have a thermostat in it.. we have replace that the radiator the water pump and its still running hot.. it didnt run hot till we put the thermostat in it..

Yes. It must have a thermostat. Otherwise it will cause problems from not warming up to the other extreme of overheating because the coolant will run too fast through radiator and not have time to dissipate heat.

Don't hate me for this guy's but I've seen the same truck run without one just it never warms up. Yes it's not good for it, builds up sludge, blah blah blah... to run no thermostat is essentially a band aid. You would need to fix the real issue, but will it run. Yes it will. If you drive this thing daily I don't recommend it long term

We would never hate you Andrew. I took the 'stat out of my '76 (390) and it went from not getting up to temp forever but when it did it kept climbing to overheated. It's my assumption that the reason is the coolant didn't stay in the radiator long enough.

Back in the day I ran my 390 no thermostat for over a year without a thermostat it didn't affect anything other than the heater doesn't work right