Design Improvements for the Zenith 601 HDS: Cowl Shape
The cowl is tightly fitted, to the extent that small bumps
are needed to accommodate the tops of the carburetors and the
exhaust pipe leaving the left front cylinder. Notice the
pronounced lip at the bottom. It makes sure that the cooling
air from the front inlet, the radiator, and the
oil cooler exits the cowl promptly. Without that lip,
proper cooling is not possible.