Chevrolet 1956 Truck Operator's Manual page 58

Then hold nut liB" and tighten lock nut "C" securely.
4. Recheck both facing-to-drum clearances.
UPPER
PEDAL
Fig. 58-Brake Pedal Clearance
Adjustment
Hydrovac Power Brakes
Description. The Hydrovac is
standard equipment on the
2 and
2lj2
ton models and
is also available as optional
equipment on all except
Forward Control models.
The Hydrovac (fig. 59) con-
Brake Pedal Clearance
Loosen nut on eccentric ad-
justing bolt (fig. 58) and rotate
bolt in direction required to
obtain correct clearance "C"
between upper corner of lower
pedal and seal. Tighten nut and
recheck clearance.
Clearance "C" should be
1 34" on L.C.F. models and
lY16"
on other models except For-
ward Control.
sists of three operating units
L.. _ _ _ _ _ _ _ _ _ _ _ _
----l
built into one assembly;
Fig. 59-Hydrovac
namely, the control valve assembly, the vacuum power cylinder
and the brake hydraulic cylinder.
With this
sy~tem
the engine vacuum is used to greatly in-
crease the hydraulic pressure to the brake wheel cylinders.
This provides unusual braking efficiency with comparatively
light pedal pressure.
Care. Lubricate the vacuum cylinder according to instructions
in the Lubrication Section.
The vacuum connections between the engine and the hy-
drovac should be checked for damage and the connections
tightened occasionally. The Hydrovac air cleaner should be
removed, disassembled, cleaned and oiled at least twice a
year and more frequently when driving on dusty roads .
• 57 •