1979 350 Auto/AC. When driving for less than 20 minutes, stopping at Gas Station, and big 'Woosh' of air comes out when unscrewing the cap. I've bought a new gas cap (vented). The Previous Owner replaced the Gas Tank and abandoned all smog. The 'Coffee Can' is still under the hood with line 'from gas tank' going into it, but no other hoses coming out to carb vacuums. I think the PO did not connect this at the tank and/or bought a 'non vented' tank.

So, can someone tell me if that 'woosh' is normal? Can I just drill a small hole in gas cap or too close to rear tail lights? (kaboom?)

 

Hi I think it Happens on my car and it hasn't given me any issue .




snaptube vidmate

 

The gas tank has a vent line, if that vent line is clogged or interrupted, no air or fuel can return to the tank. I believe the cap is vented, but it alone is not enough, perhaps a inspection of the return line will help. The VooDoo engineering on these late 80's cars is almost criminal. We all want clean air, but don't want to live like we're in Tesla-land California.