You've mentioned you don't have a baffle. Which direction does the top of the overflow tube face?? There was a service bulletin that said to carefully "form" the tube to the rear. Has this been done?? If so, install a short piece of wiper hose/fuel line to the o/flow tube to bring it up even with the top of the neck and THEN make Bill happy
and install the nail. Fill the radiator til the liquid just covers the tubes.
It shouldn't make any diff whether you're running with water, distilled, water, anti-freeze, beer, etc.
Get back to us.
paul in CT