A second set of tangs was added to the cap, and a pair of matching cam ramps to the filler tube, to provide a "first stop" position as the cap is removed to relieve built-up fuel tank pressure without risk of liquid fuel splashout.
What was the tube in the trunk for on all unibody 71's? Why was it discontinied in 72?
Nothing at all. The dome (top) of the fuel tank was changed for '72 to eliminate the need for the secondary internal chamber in the '71 (+'70 California) tanks.
