1953 CARBURETOR DESIGN
following design changes have been made on Models B, BG. and 4GC Rochester Carburetors
Model B and BC (Chevrolet
Manual and Automatic Choke)
1. The vacuum power piston on all new 1953
Model B and BC Rochester
Carburetors has been redesigned. This new design is referred to
as an "Air Bleed
Refer to figure 1
power piston differs from the previous design in that it has a hollow stem
which bleeds air into the power valve
of the Main Well Support Assembly whenever the power valve ball check
is off its seat. Air is taken
into the stem through a calibrated hole drilled through the side of the
power piston above the stem. This calibrated air bleed hole is located above the float bowl fuel level
at all times.
addition to the hollow stem and air bleed hole, the tip of the power piston stem, which contacts
the power valve ball check, is slotted. This slot permits air to bleed through the hollow stem past
the ball check valve at low manifold vacuums.
purpose of the "Air Bleed Power Piston" is simply to decrease the effect
of the metering force upon the power
restriction, thereby supplying correct mixtures at high air
2. The pump link on new 1953 Model B and BC
Rochester Carburetors is curved to accommodate a Power Glide transmission
function. This new pump link is
grooved to distinguish it from the curved link used on the Model BC Pontiac "6"
carburetors. They are not
new curved link is the same length as the straight link used on earlier model
Chevrolet Carburetors it may be used as a replacement part on these earlier models. However, the straight
link must not be used for
servicing 1953 carburetors.
3. All new 1953 Model B and BC carburetors are
calibrated using a square
approach main metering jet.
This change serves to provide the correct mixture in the upper portion of the part throttle
4. It will be noted that the new 1953 model B
and BC passenger car
carburetors incorporate a slotted vacuum spark takeoff hole rather than the
two drilled vacuum holes used on earlier models.
5. No Throttle Return Check Assembly will be
used on 1953 Power Glide cars.
However, both the carburetor
throttle lever and throttle body are designed to accommodate the return check if so
Since the 1953 Model B and BC caburetors have been completely recalibrated
for use on 1953 engines, they
must not be used to replace previous model carburetors. Always consult
the application index and
parts list for correct service parts and adjustment