Chevrolet 10 Series 1968, Service Manual, Page: 400 / 713

ENGINE FUEL 6M-7
When a more sensitive regulation is desired or if the
governor is too sensitive and inclined to surge, correct
the adjustment as follows by means of the calibrating nut
shown at "A ."
NOTE: Do not use the following adjustments
unless absolutely necessary. These adjustments
affect basic governor calibration and should only
be used if speed adjustment does not produce
satisfactory results.
Too Sensitive
1. If a governor is too sensitive or on the point of surg­
ing, remove adjusting cap and hexagonal shaft as­
sembly and place special hollow wrench A - 24283 in
position on nut "A .” Insert special adjusting wrench
A - 25264 through this wrench and turn main adjusting
screw "B" to the right one turn.
2. With hollow wrench in slot of nut “ A ,” turn this nut
to the right about 1/4 turn using the special wrench
A - 25264. The main adjusting screw "B ” must be
kept from turning while nut "A " is adjusted.
Not Stable
1. If a more senstive governor is desired, adjust main
screw "B " to the left one turn and while holding this
screw in new position, turn nut "A " to the left 1/4
turn at a time until desired regulation is obtained.
2. When adjustment is completed, tap lightly on end of
hollow wrench so that nut "A " will seat properly.
2G ENGINE GOVERNOR
(VACUUM SPINNER TYPE)
GENERAL DESCRIPTION
The Model 2G Carburetor Governor (fig. 3G) provided
with 327 and 366 V-8 engines is a mechanically driven
vacuum actuated mechanism set to govern engine speed at
4000 rpm maximum under full load conditions. With this
limit, full advantage of engine horsepower is allowed
without danger of excessive wear due to overspeeding.
This 4000 rpm limit establishes an excellent pattern for
shift control for automatic type transmissions.
The governor is comprised of two basic units; the cen­
trifugal control valve housed in the distributor (see En­
gine Distributors in Section 6Y), and a carburetor actua­
tor which is mounted on the carburetor throttle body
(fig. 4G). These two components are inter-connected by
tubing.
An engine overspeed warning device is incorporated
into the governor as shown in Figure 4G. A description
of the overspeed warning system will be found in Sec­
tion 6Y of this manual.
Operation
The function of the 2G governor is to limit engine speed
and yet allow a wider throttle opening when power is re­
quired. The throttle lever is connected to the throttle
shaft in such a manner that turning the throttle lever does
not actually force the throttle valves open but rather al­
lows them to follow the throttle lever because of the
governor spring tension. Thus when the throttle lever is
moved to wide open position, the position of the throttle
valve will be determined by vacuum on the diaphragm and
the tension of the governor or spring acting on the gov­
ernor lever.
Vacuum is applied to the diaphragm through a system
of vacuum passages and restrictions in the throttle body
and governor housing. A speed sensitive centrifugal
valve in the distributor acts as a vacuum break so that
there is no vacuum applied to the diaphragm until the
desired governed speed is reached. When the governed
speed is reached the valve is closed and vacuum is ap­
plied to the diaphragm which acts to close the throttle
valves in opposition to the governor spring tension.
When power is required as load is increased, engine rpm
will drop causing distributor valve to open and allow the
governor spring to open the throttle valves further.
F ig . 3G - Distributor and Governor Mounting
CHEVROLET TRUCK SERVICE MANUAL