Fuel tank pressure??

[akart]

I've tried to look up fuel tank pressure,not seeing a good answer. Looking @ vented caps (GM) and they say on the cap "Warning Remove Slowly Fuel spray may cause injury" What's with that, is pressure normal? Don't have a canister. have a 2 tank system but only one works,right side.Using new Stat locking cap listed for my truck.I think the frame and tank system is a 1974 K20. I'm going to drill a 1/16" hole in the cap. Any problem w/that? That pressure has to be screwing something up. Edelbrock carb and pump.Edelbrock carbs don't like high pressure. Is my fuel pressure to the carb effected??

[Dead Parrot]

Pretty sure that is a lawyer suggested CYA warning. In normal operation, the fuel tanks shouldn't have much pressure. They are normally either vented straight to the air via a differential type vent or in later versions, through the charcoal canisters.

The tanks have a LOT of slosh, especially front to rear. A cap with a hole in it will likely leak gas every time you accelerate.

[cadillac_al]

I think the only pressure that would build up is due to ambient heat. I wouldn't even worry about getting gas in my face. I never noticed much pressure in my old vehicles. After 75 or 76 GM started venting fuel tanks with a dedicated vent. I would wait to see how much pressure actually builds up on those hot days in Alaska.