Running a 4lb rad cap? Or sometimes you can find 7lb ones in stores. Try it with cap off or laying on loose and see if it boils. Where did you get a rad that skinny? Sure it's not for a "Pinto" or something small???
:p Don't new rads go for around $299 in vendors catalogs? I was looking last year for my 54 2-ton and was cheaper to buy than recore at time. Did you flush out block? Why did you need new rad? Mine was overheating even after flush, but rad was clogged at bottom and I had to have it pressure backflushed at old shop I use here. Puked out all kinds of rusty gunk that didn't even show up in anti-freeze when running. It's OK now. Course, you have new rad now, so doesn't apply. So....Never Mind!
