That part of the exhaust manifold system, on older vehicles, known as the heat riser and necessary to aid in fuel evaporation and make the transition from cold to hot idle engine operation efficiently.
The first cold day I cranked the old buggy over it was obvious the frabulator valve was rusted and frozen up as she wouldn't run right and carb touch-up adjustments made no difference.
by Robert 'Bob' Weiss November 23, 2006
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