Without a thermostat and the radiator open you should be seeing a good water flow. If you're getting it started for break in and running it before it gets up to crazy temperature put your timing light on it.
Are you doing a 2000 RPM cam break in?
If so you may want to let it heat up just a bit little bit and then bring it up a little higher and check your all in timing and put it at about 34 and then drop it down. I wouldn't run it up past 3 Grand but I would run it up to three grand just for a second to check your timing at three grand. Also check your timing at you're breaking speed as well.. something I kind of do by ear but just get it and kind of a sweet spot at the break in RPM..
