the 1973 and older vented gas fills are prone to showering gas all over when more than 3 gallons of gas are pumped in. I don't know enough to guess if installing a new style filler tube would help or what else I can do. I have checked the vent tubes (I added a 2nd vent tube and it helped) and verified they're not plugged up and nothing is attached between the main vent tube and where it connects to the top of the filler tube.
Any thoughts ?

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86 FB stock 305 Qjet South California emissions