okay, my 91 with the 318 runs normally with the temp guage at the 1/4 mark, but when I hook up a trailer and go up mountains the guage rises to 1/2 and up to 3/4, then if I go downhill it drops again back to 1/2 and then 1/4. I have changed radiator, cap and thermo valve.
Does this sound normal? I am considering going to a flex fan instead of the clutch fan.

 

When your towing or hauling your going to have a higher running temp, since the engine has to work harder. Especially when in hilly or mountainous regions. And its only worse when its hot out.
You might consider a higher-flow fan. And, if you didn't one when you changed it out, a better radiator.
Always room for improvement!

 

You can do makesure you dont have any leaks. Some may be imposible to see.

 

Stock raid. are 1 row. You canbuy 2 row. You can get a 180 deg.eletric fans to help. Make sure your raid. and ac codencer are clean. if you gotauto get an extra tranny cooler to keepit cool better.

 

i got an electric fan and it helped out pretty good, also have a tranny cooler. and i have a 180 degree thermostat in mine too.