With the holiday tomorrow and it being too hot to do anything too strenuous, I thought I'd revisit this. Please correct with exceptions. For people shopping eBay, learn here on what questions to ask...
4 barrel Firebird/Formula/Trans Am base will have almost no gap (approx. .16”(1 dime and 2 pennies)) between center hump and straight edge when you lay it across the top. Sensor and carb. vent hole should be across from, not next to, each other.
1973
Has three welded clips for vacuum hoses.
Hole for screw to hold fresh air duct is circular and only on top side.
Sensor is black.
Air flap pin exits to the right.
Trans Am PN decal (Keep your GM car all GM) is located between snorkel and indent.
Measurement between snorkel and air breather hole is 15”.
Formula PN decal (Keep your GM car all GM) is located between air breather and indent.
Measurement between snorkel and air breather hole is 14-1/2”.
1974
Went to four welded clips.
Sensor went to painted black.
Air flap pin exits to the left.
1975
Hole for screw to hold fresh air duct went oval on both sides.
Added a hole in side for vacuum switch.
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