As promised here are my findings for the repair of this Rochester B carb.
After very carefully filing just the outside screw 'ears' on both the horn and bowl (no, I didn't touch the mating surfaces (raised-lines)) and cutting new main gaskets, the two halves fitted back together almost perfectly -- no leaks.
To take care of the flooding I first inserted a vacuum pump/gauge into the inlet of the horn and determined that there was a small leak at the base of the needle valve combo.
A sanding dowel fixed the casting seat. And metal polish smoothed the brass needle and seat assembly to almost mirror finish.
After installing a new round gasket on the valve it was then installed.
The vacuum pump/gauge showed that it now held vacuum well.
The float pontoons were again tested for leaks and readjusted exactly as per specs and everything was put back together and installed on the truck.
I also reinstalled the OEM glass-dome fuel pump (after a good cleaning and set-up) and it tested at 4.5 lbs. with good volume.
The truck started up right away and ran well with no leaks or flooding.
The test drive also went ok as I ran the carb through its stages from around the block to advancing onto the highway.
The only (minor) question I now have is regarding the idle mixture screw (in the throttle base).
Before the carb problem I normally had the screw at about 1.5 turns which was about right for smooth running.
With this rebuild, the turns are now at 2.5 in order to maintain its highest vacuum (at 19.5").
While it does run well, it's this little detail that bugs me.
I can still learn to live with it though as it's just great to finally be on to another project.
Thanks all for your input
