My 1995 corvette lt1 has been overheating to the 240-250's, it has a new radiator, water pump, surge tank, resvoir, thermostat housing, thermostat, radiator cap, knock sensors. Fans do kick on when they are supposed to.
I have flushed it and bled it. It would drive fine and cool for about maybe 15 minutes when the motor is completely cool, the block(analog) sensor seems to get really hot before the digital, I've learned where the gauges should be since I know they are not linear. Then the temp spikes up and it seems like it builds too much pressure or air then shoots my coolant out the resvoir. Occasionally if i give it a few revs while moving and popping it into neutral it'll go down a tad. Any idea what could be causing this?

 

If its building that much pressure there is a good possibility you have a bad head gasket allowing combustion pressure into the coolant system.

 

Did you fill the system yourself? If so, how many quarts of fluid?