I will confess also. I had to adjust mine tighter after I filled up. But I wonder if the vapor is coming from another sorce on yours. Bad or wrong cap, charcoal canister filter plugged. Bad vaccum lines to the breather system, ecs not tight
Cap - what denotes a vented cap? I thought that, with Challengers with the ECS, none of the caps were vented?
Canister plugged - very likely, as it's original. I know that these are supposedly not serviceable, but a friend of mine told me that some guys have cut them open and replaced the filter material with stuff for acquariums. Possible? Good idea? How to reseal the canister?
I don't have a Thermoquad any more (Holley 4160), so that complicates things, as the line that would have run to the carb is open, but I don't detect any stronger odor there than anywhere else.
When absolutely topped off my gauge reads about 3/8 tank.