Chevrolet 70 1969 Series, Shop Manual

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POWER BRAKE 5-57
/ 3 6 T
Discharge Valves
Discharge Port
Gasket
Discharge Valve
Cap Nuts
Discharge Valve
Springs
Discharge Valve
Seats
Pipe Plug
Cylinder Head
Cylinder Head
Gasket
Figure 2 3 — C y lin d e r H e a d C o m p o n e n ts
Identification Tag
Exhaust Port
Unloader
Ports (3)
Reservoir
Ports (3)
Mounting
Holes
Figure 2 4 — T y p e " D - 2 " G o v e rn o r Ports
sor head by a bracket and tw o cap screws. Leave the
two cap screws loose until the air tube assembly is
tightened, then tighten the cap screws.
AIR CO M PRESSO R G O V ERN O R
DESCRIPTION A N D OPERATION
DESCRIPTION
The governor, operating in conjunction with air co m ­
pressor unloading m echanism , autom atically controls air
pressure in the air brake or air supply system between the
desired, predeterm ined m axim um , and m inim um pres­
sures. The air com pressor runs continually while the en­
gine runs, but actual com pression of air is controlled by
the governor which stops or starts com pression when the
m axim um or m inim um reservoir pressures are reached.
The “ D-2” governor as used with these com pressors, has
a piston upon which air pressure acts to overcome the
pressure setting spring and control the inlet and exhaust
valve to either adm it or exhaust air to or from air co m ­
pressor unloading m echanism.
The governor can be attached to the air com pressor or
m ounted remotely. They are adaptable to either m ou nt­
ing. C onnections in this system are to the reservoir and
com pressor unloading ports. They also have an exhaust
port (fig. 24).
OPERATION (Refer to Fig. 25)
Reservoir air pressure enters the governor at one of its
reservoir ports and acts on the area of the piston and on
top of the inlet and exhaust valve. As air pressure builds
up, the piston moves against resistance of the pressure set­
ting spring. T he piston and inlet exhaust valve move up
when reservoir pressure reaches cut-out setting of the gov­
ernor. The exhaust stem seats on the inlet and exhaust
valve and then the inlet passage opens. Reservoir air pres­
sure then flows by the open inlet valve, through the pas­
sage to piston and out unloader port to the com pressor
unloading m echanism . The air, besides flowing to co m ­
pressor unloading m echanism , also flows around the pis­
ton and acts on additional area of the piston. This addi­
tive force which results from a larger area on the piston
assures a positive action and fully opens the inlet valve.
A s the system reservoir air pressure drops to the cut-in
setting of the governor, force exerted by the air pressure
on the piston will be reduced so that the pressure setting
spring will move the piston down. The inlet valve will
close and exhaust will open. W ith exhaust open, air in the
unloader line will escape back through the piston, through
the exhaust stem and out the exhaust port.
G O V ERN O R OVERHAUL
DISASSEMBLY (Refer to Fig. 26)
1. Using cleaning solvent and a brush, clean dirt and
grease from exterior of governor.
2. Using fingers, remove rubber cover from governor as­
sembly. Rem ove two pipe plugs from governor body.
3. Using T ru-A rc pliers, rem ove cover retaining ring
from groove in governor body.
4. Rem ove adjusting screw and spring assem bly from
governor body.
5. Rem ove the piston assem bly from governor body. It
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHOP M A N U A L