Burping air from the radiator doesn't always work. There may still be a lot of air in the radiator. You may want to pull whatever fitting is in the top of your radiator (with the cooling system pressurized) and bleed air that way.
If you are not going to perform the vent system mods I've detailed in several past posts, then the second best thing to do is to install a drain cock in the top of one tank and manually vent the cooling system every once in a while. The top mounted drain cock will also help when you're filling the system .... much better results than raising & lowering the front & rear of the car.
The only other thing that comes to mind, be sure the fans are blowing air in the right direction.
-G
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