a "sandwich" type engine speed governor is to be used in conjunction with
the carburetor, be sure the carburetor has a hollow brass screw plug installed
in the extreme upper end of the power enrichment system vacuum passage.
The end of the vacuum passage is the small hole adjacent to the throttle
bore in the top of the manifold mating surface of the carburetor flange.
The hollow screw plug closes the vacuum passage leading into the carburetor
throttle bore, but permits vacuum from the manifold side of the governor
throttle plate to be transmitted to the power enrichment system. If this
plug is not installed when the carburetor is used with a governor, the power
enrichment system will not function prope rly.