Runs bad after filling tank

[Dcalebaugh]

I have an 86 that runs really bad after filling the tank. Once it gets down a little to say 3/4 it slowly gets better and by 1/2 tank runs fine. Any thoughts?

Dave:confused

 

[vetteboy86]

I think there are vent holes at the top of the filler neck, and when you slam the gas you get a slosh and could that prevent the tank from venting properly?

Just a thought.