Got it. thanks for clarification. will try that first. any idea where water t-stat is?

Its on the front of the intake manifold and under your lifting ring. No need to go there though, its working fine.

X2

sounds like the relieve valve in the block hung open and not sending the oil thru cooler..or still has 11psi relief valve in there

Not engine thermostat people stop saying that. When your ac goes out you don't fix the furnace. OIL Thermostat. And lean wouldn't really do it either only other thing too much timing or dist gear out.

Why is nobody mentioning the obvious...at 280 degrees your buzzer alarms would be screaming. Are they going off? Take the ground off the gauge and check it with the motor running.
First make sure your alarams work by turning the key to the on position (don't start it) and within 5 second or so you will hear an alarm go off.
Also, maybe the needle/gauge is stuck. I still say bad ground like when a tach doesn't read right. Try tapping on the gauge when it hot to see if it moves at all. Sounds like simple fix if your alarms aren't going off.
Try the basic stuff first before you start pulling coolers, filters and thermostats off the motor.

Oil temp... 280 degrees of oil temp... Theres no alarm for oil temp.

Whole lotta confusion going on in this thread... Water vs. oil.

agreed.

I would start with a new filter first. I have seen them collapse at high rpms.

There are alarms on oil temps, check around.

Not in any stock HP500 carb engine there isn't.