Does anyone know where the normal gauge reading(factory dash gauge) should be, mine on my 93 Lightning 5.8L only goes about 1/4 up on the gauge, never had a overheating problem, the heat takes a while to get warm, but never very hot. Any help would be greatly appreciated. John231

 

When is the last time you changed the thermostat ? I would change the thermostat to the correct one . And flush the coolant system out .

 

They don't come far off N. It's mostly for decoration.

 

Sean, that's about where the gauge points, just above the "N"

 

My 92 351W would always fluctuate, rapidly moved up to about the "R" then quickly dropped down to full cold, repeat. I took out the thermostat and found it to be failed, installed a new one, now the gauge reads right between "N" and "O" and no longer fluctuates. Heat works great. If your heat isnt so good check your heater core for being clogged, if one hose is hot and the other cold that is probably your issue.