So my 86 n/a FC is almost complete and the only thing I have left to do is figure out the cooling system. For some reason when I let the engine get up to temp while idling, the temp doesn’t stay constant but instead increases very very slowly. I’ve bled all the air out of the system, checked all the coolant levels, checked for leaks, and I’ve found none. I have the stock clutch fan and the stock radiator. Wondering if maybe I should switch to electric fan?

 

Do you have the factory plastic fan shroud fitted if so your clutch fan could be faulty

 

Either the clutch fan, the gauge itself (junk), coolant temp sensor (not likely), air in system or blockage in cooling system.
Personally I would install a aftermarket gauge and an e-fan. That's my preference. Factory stuff sucks now because of age.
Take care of the issue before it causes a more costly issue. Fix it first.

Edit: With a mechanical fan you must have the shroud too like said above.

 

dont rely on the stock gauge. simple. if it IS overheating, check to make sure your thermostat is opening as well.

 

Cracked plates are always the problem for the engines I have taken down.