4 or 6

[Keith True]

If you speed the water flow up too much it drops down through the core,then back to the block without transferring it's heat.If you shoot the heat number at the top of the core while running,then the bottom of the core while running,there should be a substantial difference in temperature.If the temp difference isn't a lot,then the water is running through it too fast,or the radiator still isn't working right,new or old.