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“gotcha’s” that often bites a novice carburetor rebuilder is float
non-interchangability on Carter WCFB and Rochester 4-GC carburetors. Both Carter and
Rochester engineers determined that, on some applications, the float level in
the primary side of the carburetor should be different than in the secondary
side of the carburetor. Maximum float buoyancy is generally accomplished when
the float pontoons are at a 90-degree angle to the fuel valve. To accomplish
the maximum buoyancy AND have different levels, DIFFERENT FLOATS WERE
OFTEN USED IN THE SAME CARBURETOR! Once, I checked the various Rochester
floats that I had in my inventory, and at the time I had 19 DIFFERENT floats
for 4-GC carburetors. I never counted the different Carter floats but there
are more than a couple. Now, tooling for
different parts costs money, so one way different floats were made was to use
the same arm, the same pontoons, AND SOLDER THE ARM TO THE PONTOONS AT A
DIFFERENT HEIGHT! Unless one is
looking for this, the floats look to be identical, but when re-installing,
one will find massive re-adjustment may be needed. Placing the different
floats side-by-side will reveal the differences in height of the arms. This
is NOT an error in manufacture; but by design. If the floats are
interchanged, it may be possible to get a correct “static” setting, but the
fuel level in the bowl may be incorrect as the buoyancy of the float may not
shut off the fuel at the correct level. Some of the
Carter secondary floats have cutouts in the pontoons for the auxiliary
airvalve, so these are quite obvious; but the ones with the same pontoons are
not obvious unless one looks for them. When rebuilding
one of these carburetors, always nice to have the original bill-of-material for
the carburetor to determine if the floats SHOULD be the same or different
(one cannot count on a previous rebuilder knowing of this issue). In the absence of
the bill-of-material, one should pay attention to the height of the arm on
each float, and if different, mark each float as either primary or secondary. |