ok i have a .030 over 305 10:1 compression iron heads... it runs at 215 just cruisin around and 245 in traffic.. new water pump, electic fan on a switch on all the time, 160 thermastat, and new radiator, and i have the air dam on.. also with the cap off if i start it, it will puke out the rad, im running straight water also ... im thinking headgasket... any other ideas??

 

run coolant not straight water

 

What difference do you think that would make, exactly?

 

over time water boils off and the anty freeze is a cooling and lubricating agent

 

try running a bigger fan

 

It shouldn't be reaching a temperature that would allow it to boil in the first place, although I will admit antifreeze is a lubricating agent that you should have for the health of your water pump, I will also say that it should make no difference in this situation.

 

antifreeze has a lower freezing emp and higher boiling temp, so when your engine gets hot the water boils off, because operating temp is higher than waters boiling point, thats why antifreeze is used

 

Check timing.

 

Make sure your fan is blowing the right direction. The first time I pulled my rad and fan, I plugged it in wrong and it ran backwards. Just a thought.