Considering the age of your jeep, and if it hasn't been flushed on a regular basis, you may need to have the radiator rodded to remove the calcium build-up. The best thing to run in a radiator is antifreeze and distilled water, but we all get lazy and put tap water in them. The build-up will seriously obstruct the flow of water. Sometimes the cost of rodding one is so close to just buying a new one that it isn't worth it. Therefore, ask for a price first and compare it with the cost of a new radiator.
Also, you may check your lower radiator hose to make sure it has a spring inside of it. Without one, the hose can collapse due to the suction when the engine is running at high rpms (high flow).
These are the two simplest suggestions I can make. Timing that is set too low (not enough advance) makes the engine run hotter, but we're probably splitting hairs at that point. You can keep that in mind, though, if these first two suggestions are null.
Currently an '86 CJ-7---following a string of '01 Sahara, '90 Sahara, and '85 CJ-7. Finally got back to how it all began....