Looks like I’ll have to pull the cores, and drill through the blocking plate.  That would have been a much easier job before the AN-16 bungs were welded on, but I can still get a ¾” hole saw through the opening, so it should be possible.

 

 

That should work fine, and at least it explains why it's acting the way it is.  Good thing you didn't try to fly it that way.   You are to be applauded for being cautious, and observant.  

 

I heard a saying a long time ago that stated “its better to be down here wishing you were flying, than to be up there wishing that you were on the ground” or something to that effect.  I’ll fly with some things not at 100%, but not anything engine related.  (or wings, controls, brakes, and several other required items)

 

 

 

Do you know what vehicle those cores came from?  I know the Chevy Caprice cores from 77-90 do not have any sort of dividers in the tanks.  Here's my favorite evap core page- http://www.frigidair.net/Parts/product_EV.html

 

One was for a 1990 Camaro IROC Z28.  The other for a 1995 Corvette.  These were new cores, but I think were aftermarket or OEM.  The boxes did not say AC Delco on them.  They seem to be very well made, but obviously with at least one exception with the block in the one tank on each core.

 

Regards,

Steve