[Formulajones]

On the vented caps, and I'm talking the originals, they vented both ways back in the day, on the pre 1970 stuff. I remember when these cars were new, if you filled them up yes they could spill a little fuel on a hard acceleration. It was never a big deal. They never did stink in the garage either, still to this day I can't tell a difference in that regard anyway.

Repop vented caps don't do that, they only vent inward. I tend to believe the manufactures are restricted and can't make them vent outward due to regulations put in place long after these cars were built

Because of that I had to seek out nos caps at swap meets for our older cars that vent in and out. These keep pressure from building after shutdown, especially when it's hot outside. I suspect that's a possible problem with some of you guys having hot start issues too

My 70 formula has its original vented cap, it vents both ways and yes it can trickle fuel out on a hard launch if I have the tank filled to the top. My 69 z also does the same thing.

When I'm at the track I just shove a shop rag behind the license plate so I don't splash the starting line. Not a big deal really, been dealing with that for 45 years. It's how these cars were. Dad bought his 69 GTO new, still has its original cap, and it vents in and out, and yep it'll spill fuel when the tank is topped off. It's been like that since it was brand new.