400 BB build issues

After all the stuff we had on the slant overheating thread.... :D

I think he is getting steam pockets in the heads like my 440 Demon did before I put the 195 T-stat in it. I also drilled the little hole in the outer ring so the air could bleed out easily. You want the cap on so you can keep things under pressure and won't boil so easily. There is a bypass hole below the thermostat in some of the pump housings. I plugged mine with a 1/2" expansion cup after making sure the hole was the proper size. You definitely want all the air you can flowing through that radiator.