340 with edelbrock heads overheating

took thermostat out . ran the car with out radiator cap. heated up again over 210 and rising. Coolant flow looked great, i did see lots of bubbles. I am thinking I have exhaust in the coolant. Cant think of what else it could be at this point.

btw, its not the radiator, it was doing the same with the radiator i had in it before the cam and head swap. i only changed radiators after the problem persisted.