Written by Moore Good Ink
The Goggle valve is a mechanically operated secondary throttle plate with a unique goggle-like profile. Normally a carburetor’s secondary throttle arrangement would take the form of two round bores. But because the Street Demon is designed to fit intake manifolds of both spread-bore and the smaller square-bore patterns, air flow would have been severely restricted by a conventional two-bore secondary arrangement.
To maximize the air flow Demon created the Goggle valve. “Without it,” declared its designer Larry Tipton, “generating air flow of up to 750cfm would have been almost impossible.”
The Goggle valve’s unusual shape was conceived after investigating numerous OEM and aftermarket intake manifolds. By necessity its arc of travel from closed to fully open has to accommodate a variety of divider walls and, obviously, Demon was keen to avoid adding any unwanted spacers. These were the conditions that influenced the Goggle valve’s unusual shape.
Connected to the primaries by a progressive linkage, the Goggle valve is timed to start opening approximately 30 degrees after the primaries. As expected, its faster ratio of movement brings it to the fully open position at the same time as the primaries.