High Speed System - Ford LRG-423 Service Manual

03-26 Auxiliary Systems 03-26
ZENITH MODEL #33 CARBURETOR OPERATION AND SERVICE (Continued)
system. It cannot be said that the idle system ceases
to deliver fuel entirely at wide open throttle, but it must
be made clear that the amount of fuel delivered from
the idle system at wide open throttle is minute and
relatively unimportant.
High Speed System
The high speed system consists of a venturi, a main
jet, a well vent, and a well tube. This system also
controls the mixture at part throttle speed.
The main jet controls fuel delivery from about one-
quarter to three-quarters throttle opening. To maintain
a proper mixture ratio, a small amount of air is
admitted through the well vent. There are also air
bleed holes located in the well tube at a point below
the level of fuel in the well. Introducing air into the well
tube below the level of fuel, reduces the surface
tension of the fuel and helps fuel flow at low suction.
This bleed also restricts fuel flow through the main jet
under high suctions.