Engine What Radiator Cap?

I'm almost certain i burped every bit of coolant out of the motor after changing the intake gaskets.

So here's the issue. If parked the car will stay dead on 180. (where its supposed to be) If i start driving it will creep up to around 210. Even on the highway. I have a Stant vented radiator cap. 16psi. I lift the vent arm with the car reading 210 and nothing. I unscrew the cap and no pressure. I'm not losing coolant. So i figure my Stant took a dive.

Brand...

I've seen Motorad and Stant vented caps. I'm not excited about the stant cap using plastic inside the cap. I'm not sure if the valving on the Motorad is plastic or metal. I'm open to other brands but i like the venting feature.

Psi...

I did some googling on this but wanted to know what you guys are doing. They say 16psi caps were introduced when higher temp thermostats were introduced for emissions purposes. I use a 180 degree thermostat and my SCT chip is programmed to kick the fan on at 180. The argument for a lower PSI cap is supposed to be that the higher pressure puts higher pressure on everything from hoses to gaskets and if you don't run above 180 then a 13psi is better.

I just wanted to see what you guys say. Recommendations welcome.

Chris

I have an electric autometer gauge with a sensor at the drivers side front of the intake lower. I know it works fine because the fan kicks on at 180 as its been doing always. I also confirmed the temps with a laser thermometer. I know it sounds crazy but the motor will get just under the 210 mark and will have no pressure. revving it with the cap off does show the coolant is moving but at idle with the cap off it never overflows.

BTW the Boiling point of water is 212....and have Mark viii fan on the radiator itself. That's probably why its not boiling.