[William]

The ZL1/4346 story is documented by two sources. The August 1969 Hi-Perf Cars test of #3 with engine bay photos with the air cleaner removed. When Bill Porterfield was researching the car he obtained the orginal photo and had it englaged such that the carburetor part numbers were legible. This was recounted in John Hoopers 1991 Camaro book. Fred Gibb was interviewed for the story and recalled that the #1 car failed tech at at AHRA meet because it did not have the 850 carb as listed in the AMA specs. Chevrolet sent him correct carbs for the ZL1s he still had in stock.

The OE "flat bottom" ducted hood air cleaner as used on SHP bbs and Z/28s had a 90º vent tube. If mounted on a Holley double-pumper carb the tube will contact the rear pump lever. Chevrolet later redesigned the tube with 2 45º bends to clear the pump. I do not know that this was why the cars were built with 780s.

The ZL2 special ducted hood was included with COPO 9560 and 9561. Racers often removed the valve and did not use a filter.