Sidekick overheating problem

I just replaced my 92 Suzuki Sidekick's cylinder head with a rebuilt one. I replaced all the hoses and water pump and flushed the cooling system also. Now it overheats. With the thermostat removed there isn't a constant flow though the top of the radiator while looking with the cap off but flows when reved. Any help would be greatly appreciated.

have you checked your fan belt?
I've had the same problem with mine slipping and overheating as a result its usually fine at an idle and begins to overheat with acceleration