I started my 455 cutlass for the first time today. I initially wasn't getting fuel to the carb. At first, I thought it couldn't pull gas because the tank vents were both plugged with bolts. I opened the gas cap and it let out a whoosh. I left the cap off and still couldn't get gas. It turned out to be a clogged fuel line. But it got me thinking. Was it common to plug the vent lines at the tank? Should I uncork one (or both)?

 

When you pulled the cap off it went whoosh. That makes me think you should have the vent hoses open, with a filter on the ends. But I'm not an expert, that's just what occurs to me. John

 

You need to either install a vented gas cap, or properly hook up the vent lines.