1991 honda civic the stock radiator cracked and thermostat went bad. I put a 91 integra radiator in it got it all back together but now its getting to much pressure in the system, so i pulled the thermostat hoping that would let it flow better and just run cooler. Well it still is just boiling the coolant out. water pump is fine,head gasket was replaced not to long ago. the only thing i can really think of is:

a: my fan is not kicking on all the time but it does kick on

b: the stock civic upper and lower rad hoses are smaller diameter than the integra ones and causing pressure to back up not being able to flow right.

what do you think it could be? im out of ideas.