BOS / SAV EMISSIONS - 5F-390-823225--1 1096
Description
The Bodensee Emissions system is designed to
lower exhaust emissions to meet regulations on the
“Bodensee”. It consists of the following items: a
Positive Crankcase Ventilation (PCV) circuit, a
Ported Vacuum Switch (PVS) circuit, a higher
temperature thermostat [160°F (71°C)], and a
specially designed Weber WFB carburetor.
Weber WFB carburetor is unique in design, as the
main body and flange are cast as a one piece unit.
This, along with the bowl cover, make up the two
piece construction which is made of light, durable
aluminum to dissipate heat.
There are two separate float circuits. Each float cir-
cuit supplies fuel to a primary low speed circuit and
a primary and secondary high speed circuit. The
bowls are vented to the inside of the air horn. A con-
necting vent passage effects a balance of the air
pressure between the two bowls.
The float needle valves are installed at an angle to
provide the best possible seating action on the
needles. This provides better needle response to
float movement, also.
The PVS circuit is used in conjunction with the idle
circuit. When the engine is cold, the PVS circuit is
closed. This shuts off a metered air-bleed to the idle
circuit, to maintain a rich idle circuit for warm-up.
Once the engine warms up [approximately 128°F
(54°C)], the PVS opens, allowing a metered amount
of air to be mixed into the idle circuit. This leans the
idle circuit to the proper operating air-fuel ratio.
The high speed circuits use staged step-up rods in
the main metering jets to control the amount of fuel
admitted to the nozzles. The position of the step-up
rod is controlled by manifold vacuum applied to the
vacuum piston.
A primary air bleed located in the venturi cluster pre-
vents a rich condition or bog as the high speed circuit
is reactivated after deceleration.
Small “L” shaped metal tabs, called “distribution
tab(s),” are attached to some venturi clusters and
protrude into the air stream at the proper location to
aid distribution of fuel on selected applications.
The PCV circuit ventilates crankcase vapors (un-
burned gases) back into the intake manifold to be
burned again.
Special Notes
IMPORTANT: Disassembly and repair of the Bo-
densee Emissions carburetor is basically the
same as the other Weber WFB carburetors. There
are some internal and external differences that
are noted following:
Carburetor Top Cover
The carburetor top cover (air-horn) has vacuum fit-
tings for connection to the “Ported Vacuum Switch”
(PVS). The 5.7L version also has a fitting for the fuel
pump sight tube.
73701
a
b
a - Vacuum Fittings
b - Fitting for Fuel Pump Sight Tube (5.7L ONLY)
Sealed Idle Mixture Screws
The idle mixture screws have seals that prevent tam-
pering with the idle mixture after the mixture has been
properly adjusted.
71798
a
a - Screw Seals
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