<VV> Gas fill problem

[Rick Loving]

I picked up my new 66 Corvair coupe today.  While talking to the PO, the
subject of gas came up as it is a turbo and I was wondering what octane
he had been using.
 
Apparently it jarred his memory about a little quirk regarding the gas
filler neck or tank on the vair.  He mentioned that if you try and fill
it fast, it backs up the neck and you have to fill it slow.  I told him
I had a similar issue on one of my previous vairs and that if I turned
the nozzle upside down it would fill faster.
 
On my way home I stopped to get gas, stuck the filler arm in upside down
and proceeded to begin to filler-up.  Within about a second, I heard the
strangest gurgle and gas blew back all over out of the filler.  
 
Shocked I tried again only to have another blast of gas come gushing
out.  I tried several times, each time applying less and less pump
pressure, with the end result being gas backing up and glogging out with
a burp and spray.
 
Finally I had the pump on trickle and proceeded to fill the car up after
standing there for 10 minutes with cramped fingers.  I couldn't depress
the lever enough to set the lock so I had to hold it and let off
everytime I started to hear gas backing up the neck.
 
How do I correct this?
 
I assume that there should be some sort of vent ot passage to allow the
flow of gas to run smoothy down and that this little feature is either
missing or clogged.
 
What do I look for?
 
Rick Loving