Chevrolet 40 Series 1972 User manual

40-60 SERIES TRUCK
SUPPLEMENT
SERVICE MANUAL

1 9 7 2
CHASSIS SERVICE MANUAL
SECTION INDEX
SECTION NAME
0LUBRICATION
SUPPLEMENT 3FRONT SUSPENSION
c o v e r in g 4REAR SUSPENSION
SERIES 40-60
CHEVROLET TRUCKS 5BRAKES
6A GASOLINE ENGINES
FOREW ORD 6D ENGINE MOUNTINGS
6K ENGINE COOLING
SYSTEM
This manual is a supplement to the 1971 Series 40-60
Truck Service Manual. It includes procedures for main
tenance and adjustments, minor service operations, and
removal and installation for components of Chevrolet Series
40 through 60 Trucks. rocedures involving disassembly
and assembly of major components for these vehicles are
contained in the 1972 Chevrolet assenger Car and Series
10-30 Truck Overhaul Manual or the 1972 Series 40-60
Truck Overhaul Manual Supplement.
This manual should be kept in a handy place for ready
6M ENGINE FUEL SYSTEM
6T AIR COMPRESSOR
AND GOVERNOR
6Y ENGINE ELECTRICAL
reference. If properly used, it will enable the technician to
better serve the owners of Chevrolet built vehicles.
All information, illustrations and specifications con
tained in this literature are based on the latest product
information available at the time of publication approval.
The right is reserved to make changes at any time without
notice.
7TRANSMISSIONS
AND CLUTC ES
STEERING SYSTEM
10 W EELS & TIRES
11 S EET METAL
CHEVROLET MOTOR DIVISION
General Motors Corporation
DETROIT, MICHIGAN
12 C ASSIS ELECTRICAL
AND INSTRUMENTS
ALP ABETICAL INDEX
© 1 72 General Motors Corporation Printed in U.S.A.

Sec. 0
Page 1
SECTION 0
Jluhnicatio-n
All information contained in Service Man al ST -331-71 nder
LUBRICATION (SEC. 0, Page 1 thro gh 12) will apply to vehicles cov
ered by this p blication. The following information will also apply:
TRANSMISSION CAPACITY CHART
Man al Transm ission U.S. IMP.
SM465 86%
NP435 75%
NP540 9 U
NP542 10 8%
CL282 12 10
CL285 12 10
CL325 14 11%
CL327 14 11%
SP5652 13 10%
SP5752 15 m
SP5756 15 12%
A tomatic Transm ission
MT40 18* 15
MT41 18* 15
AT475 10* 8l4
AT540 22* 18%
* Filter Change Only.
A xiliary Transmission
SP6041 86%
SP7041 11 9%
ENGINE OIL
(SYMBOL “E” ON CHARTS)
ENGINE OIL
It is recommended that new engines sho ld
have the first oil change at 3,000 m iles, thereafter
at 3 months or 4,000 mile intervals. This drain
interval may be increased or decreased depending
pon the severity of service and experience with
specific oils or the recommendations and sed oil
* analysis as f rnished by the s pplier. S ch a pro
ced re wo ld be helpf l in establishing the most
practical oil change period for the partic lar
service. Refer to Service Man al ST-331-71.
Contaminated engine oil can ca se a malf nc
tion of valve lifters or the PCV valve. A sticking
valve lifter can ca se leakage of nb rned gases
thro gh the valve. A pl gged or sticking PCV valve
will affect carb retor mixt re and will prevent
proper crankcase ventilation.
ENGINE OIL FILTER
Oil filter sho ld be replaced at the first oil
change and each oil change thereafter to filter
sm all particles which co ld affect valve lifters or
PCV valve action.
RECOMMENDATIONS
The oil ind stry markets vario s types of en
gine oil nder certain service designations and
specification n mbers.
The selection of a reliable s pplier, with close
attention to his oil and filter element change rec
ommendations can provide satisfactory l brication
and longer life for engine.
Gasoline and D iesel Engines
Use only high q ality oils which are intended
for Service Designations "MS” and "DM” (SE/CC
New A.P.I. Designation) see NOTE.
The following additive limitations, which re
q ire emphasis, have been placed on the recom 
mended MIL-L-2104B (now s perseded by MIL-L-
46152) and S pplement 1 oils:
1. S fficient zinc dithiophosphate to prod ce
a minim m of 0.07 and a maxim m of 0.10 per
cent by weight.
2. S lfated ash (ASTM D-874) of 1.00 per cent
maxim m by weight, except l bricants that contain
only bari m detergent-dispersants where 1.50 per
cent by weight is allowed.
NOTE: S pplement 1 engine oils (based pon
now obsoleted MIL-L-2104A) have been s perseded
by MIL-L-2104B engine oils. However, S pplement
1 engine oils MS-DM (SE/CC New A.P.I. D esig
nation), with a history of satisfactory performance
are available, and may be sed.
The se of proper engine oils and oil change
intervals are yo r best ass rance of contin ed re
liability and performance from yo r engine.
IMPORTANT: Non-detergent and other lower
q ality engine oils are specifically not recom 
mended. POWER STEERING FLUID
(SYMBOL "S32”)
GM Approved Hydra lic Power Steering Fl id
is available thro gh wholesale wareho ses and tr ck

Sec. 0
Page 2
LUBRICATION
centers. Check fluid level every 6,000 miles or 4
months, hichever occurs first. Fill pump reser
voir to proper level. If GM Po er Steering Fluid is
not available, DEXRON® Automatic Transmission
Fluid (Symbol SI9) may be used.
CAUTION: DO NOT use GM Power
Steering Flui in automatic transmissions.
AUTOMATIC TRANSMISSION FLUID
(SYMBOL “SI 9” ON CHARTS)
(Refer to Service Manual ST-331-71)
Oil level in the automatic transm ission must
be checked at each engine oil change. Under normal
driving conditions the transm ission fluid should be
changed every 24,000 m iles. Under unusual condi
tions such as off-road (construction) or constant
stop and go driving (pickup and delivery) fluid
should be changed at 12,000-mile intervals. It is
important that transmission fluid level be main
tained at the full mark and NOT OVERFILLED.
ENGINE AND ACCESSORY
LUBRICATION
The follo ing additional information applies to
Lubrication Chart (fig. 4) on page 7 of ST-331-71
Service Manual.
CARBURETOR AIR CLEANER
ELEMENT
Air cleaner should be inspected and serviced
at intervals specified in Emission Control System
booklet, or more often under severe dust conditions,
also, henever dirt is visible in element or oil.
POWER STEERING RESERVOIR
Fluid level should be checked every 6,000
m iles and filled ith S32 Po er Steering Fluid, or
if not available ith S19 Automatic Transm ission
Fluid.

Sec. 3
Page 3
SECTION 3
S u d s K t & n d A X U l
SECTION 3A
f y n x w U A U < f * u n e + t t
All information and alignment instr ctions in Service Man al
ST-331-71 "FRONT END ALIGNMENT” (SEC. 3A) are applicable
to models covered by this s pplement.
SECTION 3B
A xle.
All front axle information in Service Man al ST-331-71 "FRONT
AXLE” (SEC. 3B) is applicable to models covered by this s pplement.
All front axle information for the F-120 axle is also applicable to the
F-110 axle. Ill strations and specifications have been pdated.
1 Steering Kn ckle 9 Axle Center
Spindle 10 Stop Bolt and Lock
2 Kingpin B shing N t
(Upper) 11 Draw Key
3 Kingpin 12 Thr st Bearing
4 Cap Screw 13 Tie Rod End Assy.
5 Kingpin Bearing Cap 14 Kingpin Bearing Cap
(Upper) (Lower)
6 Gasket 15 Gasket
7 L be Fitting 16 Kingpin B shing
8 Shim (Lower) t-8793
1 Steering Kn ckle
Spindle
2 Steering Kn ckle
B shing
3 Kingpin B shing
(Upper)
4 Kingpin
5 D st Cap
6 Kingpin N t
7 Cotter Pin
8 Gasket
9 L be Fitting
10 Washers or Shims
11 Axle Center
12 Stop Bolt and Lock
N t
13 Thr st Bearing
14 Tie Rod Assembly
15 Pl g Retainer
16 Ejqpansion Pl g
17 Kingpin B shing
(Lower) t-8794
Figure 1 —Steering Knuckle (F070 Axle) Figure 2 —Steering Knuckle (F090 Axle)

Tr o n t axle
Sec. 3
Page 4 ___________
T-8795
1 Steering Knuckle
Spindle
2 Steering Knuckle
Bushing
3 Kingpin Bushing
(Upper)
4 Kingpin
5 Cap Scre
6 Dust Cap
7 Kingpin Nut
8 Cotter Pin
9 Gasket
10 Lube Fitting
11 Spacers or Shims
12 Axle Center
13 Stop Bolt & Lock Nut
14 Thrust Bearing
15 Tie Rod End Assy.
16 Plug Retainer
17 Expansion Plug
18 Kingpin Bushing
(Lo er)
Figure 3— Steering Knuckle (FI 10 and F I20 Axles)
AXLE SPECIFICATIONS
AXLE MODEL F050-F055 F070 F090 F110—FI 20
KING PIN
Length
.................
6.3594” 7.8906” 8.750” 8.750”
Diameter
At T p ...............
1.1090”— 1.1094” 1.2492”— 1.2496” 1.1855”— 1.1865” 1.1855”— 1.1865”
At B tt m ...........
1.1090”— 1.1094” 1.2492”— 1.2496” 1.14330”— 1.14340” 1.4330”— 1.4340”
KING PIN BUSHING
Length .................
— —
1.9063” 1.9063”
Diameter
Outer ................
— —1.4330”— 1.4340” 1.4330”— 1.4340”
Inn er
.................
——1.1870”— 1.1880” 1.1870”— 1.1880”
STEERING KNUCKLE BUSHING*
Length .................
Upper ................
1.3438” 1.875” 1.709”— 1.729” 1.760”
L wer ................
1.3438” 1.875” 1.990”— 2.010” 2.150”
I.D. When Installed .... 1.1094”— 1.1124” 1.2496”— 1.2526” *1.4365”— 1.4375” 1.434”— 1.437”
STEERING KNUCKLE TO AXLE
CENTER CLEARANCE 0.005” 0.005” .004”— .012” .004”— .012”
.114”— .116” White .114”— .116” White
SPACING WASHERS AVAILABLE
— —.121”— .123” Yell w .121”— .123” Yell w
.128”— .130” Blue .128”— .130” Blue
SPACING SHIMS AVAILABLE.. 0.005” 0.005” 0.005”
_
0.010”
TORQUE SPECIFICATIONS
King Pin Nut ...........
_ _
250 Ft. Lbs. then 250 Ft. Lbs. then
Advance t Next Advance t Next
C tter Pin H le. C tter Pin H le.
King Pin Bearing Cap, Cap
Screw ................
4 -5 Ft. Lbs. 5 -6 Ft. Lbs. 3 - 5 Ft. Lbs. 3 - 5 Ft. Lbs.
* Ream after Installati n

SECTION 3C
f y n & n t f J U w a A .
All information on Front Springs contained in Service Man al
ST-331-71 “ FRONT SPRINGS" (SEC. 3C) is applicable to models
covered by this s pplement. The following “ Torq e Specifications”
chart has been pdated.
TORQUE SPECIFICATIONS
C-M-S
Models
(Ft.-Lbs.)
T
Models
(Ft.-Lbs.)
Spring U-Bolt (N t)................................................. . . 105 - 130 190 - 210
Spring U-Bolt (N t)................................................. . . *175 - 250 -
Spring Hanger to Frame Bolt (N t) ..................
60-85 35 - 45
Spring B mper to Frame Bolt (N t) ............... 14-22 35 - 45
Spring B mper to Frame Bolt (N t) ...............
** 2 - 3 -
Spring Front Eye Bolt (N t) ..............................
. . 190 - 210 150 - 200
Spring Rear Rebo nd Pin Retainer (Bolt) . . . 20 - 25
Spring Rear Rebo nd Bolt (N t) ........................
75-95 -
Shock Absorber Bracket to Frame Bolt (N t) . . 40-50 65 - 95
Shock Absorber Upper and Lower Eye Bolt (N t) 65 - 95 40 - 50
Shock Absorber St d to Frame (N t)................ 130 - 190 -
* 9,000 and 11,000 lb. Axles Only.
** 366 and 427 V8 Gas Engines.
SECTION 3D
c J lu b i a n d Q e a s U n G A .
All information in Service Man al ST-331-71 “ FRONT HUBS AND
BEARINGS” (SEC. 3D) is applicable to models covered by this s pple
ment. The following revision will also apply:
CLEANING, INSPECTION, AND REPAIR
REPAIR
Brake Dr m Replacement
1. Demo ntable Type. The demo ntable type dr m may be separ
ated from the h b and removed from the vehicle witho t dist rbing the
h b. The dr m is held to the h b by the wheel st ds and n ts as shown
in fig re 4.

Sec. 3
Page 6
FRONT HUBS AND BEARINGS
T-91 15
Side Ring
Lock Ring
Wheel
Wheel Stud Nut
Wheel Stud
Brake Drum
Hub
Cap Scre & Washer
Bearing Cone and
Roller Assy. (Outer)
Bearing Retainer
Adjusting Nut Washer
Adjusting Nut
Hub Cap
Cotter Pin
Backing Plate
Inner Oil Seal
Bearing Cone and
Roller Assy. (Inner)
Spindle
10
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
9
Figure 4 — Front ub and Bearing with Demountable Wheel and Drum

Sec. 4
Page 7
SECTION 4
( le a / i S u A s n e t t & io s t
All information contained in Service Man al ST-331-71 is ap
plicable to models covered in this s pplement. The following informa
tion will also apply:
SECTION 4A
(lean. A xleA . a n d G ottisioh
IMPORTANT
When parking vehicle eq ipped with a two- or three-speed axle, the
axle sho ld be shifted into LOW range with engine r nning. Engage
cl tch and transmission to be s re axle has completed shift into LOW
range. Apply parking brake, place transmission in ne tral and sh t off
engine. When leaving the vehicle parked or nattended the previo s in
str ctions m st be followed:
VACUUM SHIFT SYSTEM
MAINTENANCE
AIR CLEANER
Air cleaner removes dirt particles from at
mosphere which passes into the control valve and
other nits. Air cleaner sho ld be removed and
cleaned at reg lar intervals.
SERVICING AIR CLEANERS
(Refer to Fig re 1)
The air cleaner sed on Conventional and S50
Models is the metal c p type which ses a hog's
hair type element. This c p is a friction fit on the
air intake pipe and can be removed by p lling
straight off. It can be cleaned by rinsing in a s it
able solvent and re sed. Refer to LUBRICATION
(SEC. 0) in this s pplement for service intervals.
If cleaner has become so laden with an acc m la
tion of dirt, that satisfactory cleaning cannot be
done, replace with a new cleaner.
The air cleaner sed on all Tilt-Cab Models
is a plastic encased, synthetic element type filter,
and cleaning is NOT recommended. When cleaner
becomes so laden with dirt, that tapping it against
som e solid s rface (s ch as a work bench) will
not remove foreign matter, then a new cleaner
sho ld be installed.
IMPORTANT: DO NOT OPERATE VEHICLE
WITH AIR CLEANER DISCONNECTED OR RE
MOVED. Figure 1—Air Cleaners
T-9142
AIR TYPE ELEMENT
PLASTIC OUSING SYNT ETIC ELEMENT
)

Sec. 4
Page 8
SECTION 4B
(leal BpAitUfi and Suifiesutiott
HENDRICKSON TANDEM REAR SUSPENSION
Refer to Service Manual ST -331-71 "REAR SPRINGS AND SUS
PENSION” (SEC. 4B), pages 4B-7 and 4B-8 for figures 9, 11 and 12.
EQUALIZING BEAM REMOVAL
AND REPAIR
The follo ing procedures cover removal and
installation of either equalizing beam ithout re
moving any other units of the suspension system .
When removing an axle assembly, accomplish only
steps required to loosen axle at each end of beam.
EQUALIZING BEAM REMOVAL (Fig. 9)
1. Raise and support frame to remove eight
from beams.
2. At axle brackets, remove nuts (5), ashers
(7), and bolt (1). Pry adapters (2) from bushings
and brackets.
3. With blocking under beam cross tube (fig.
1) to support eight of beams, remove saddle caps
attached ith four nuts and flat ashers.
4. Lo er the cross tube and beams, then slide
beams from tube ends.
EQUALIZING BEAM INSPECTION
1. Inspect beam end bushings and beam center
bushing for evidence of damage or deterioration of
the rubber. If any damage is evident, replace bush
ings as directed under "Equalizing Beam Bushing
Replacement" later in this section.
2. Inspect cross tube and thrust ashers and
replace if bent or orn.
EQUALIZING BEAM BUSHING
REPLACEMENT
Press old bushing out, using a suitable driver
or press to exert force on bushing outer sleeve.
Press ne bushing into place, exerting force on
bushing outer sleeve until outer sleeve extends an
equal distance through beam at both sides.
EQUALIZING BEAM INSTALLATION
(Refer to Fig. 9)
1. Position beams, ith cross tube and thrust
ashers in place at spring saddles and axle brackets.
NOTE: At axle end of beam, install adapters
(2, fig. 9) at each side of bracket and into bushing.
IMPORTANT; The cut-off (flat) side of each
adapter must be located in a vertical position as
sho n in figure 11.
2. Install bolt and asher through adapter and
axle bracket at each end of equalizing beam (fig. 11).
NOTE: Install bolt and asher from inner side
ith nut located to ard heels (fig. 11). Tighten
nuts or bolts to torque listed in "Specifications" at
end of this section. Figure 12 sho s section through
mounting.
3. Install spring saddle caps to attach beam
center bushing to spring saddle. Install saddle cap
stud nuts or cap scre s and tighten to torque listed
in "Specifications" at end of this section.
1Beam Center Bushing 7Setscre
2 Spring Saddle 8 Equalizing Beam
3 Spring Assembly 9Cross Tube
4 Spring Saddle Top Pad 10 Spring Saddle Cap
5 Top Pad to Spring 11 Stud
Saddle Bolts 12 Thrust Washer
6Lock Nut 13 Bushing
Figure 1— Section Through Spring Saddle and Beam

Sec. 5
Page 9
SECTION 5
lin & k e A ,
All information in this section in Service Man al ST-331-71 also
applies to vehicles covered by this s pplement, except as specifically
stated in the following proced res:
SECTION 5A
< M - t^ d n < u c U c B ' l a h e i .
BRAKE SYSTEM MAINTENANCE
CHECKING FLUID LEVEL
A sticker (fig. 1) reading "CHECK BRAKE
FLUID LEVEL EVERY 30 DAYS OR 3000 MILES”
is affixed to the cover of each brake master cyl
inder. Fig re 2 ill strates a typical cover with the
sticker applied.
Fl id level sho ld be maintained to within V2"
of top of master cylinder reservoir.
VACUUM GAUGE
Two vac m ga ges are sed oft some ve
hicles. Two ga ges are standard eq ipment on all
■
school b ses (d al-split-brake system) and optional
on all other vehicles eq ipped with d al (split)
brake system s. These ga ges are mo nted on a
special bracket below the center of the dash panel.
One ga ge is connected to one vac m system
of the d al brake system and the other ga ge is
connected to the other vac m system . Vac m
ga ge readings may differ d ring operation of the
vehicle. However, if the readings differ by ten
inches of merc ry or more for an extended period
of vehicle operation the vac m system s sho ld be
checked immediately to determine ca ses. If the
vac m ga ge is s spected of being fa lty, check
ga ge according to instr ctions in Service Man al
ST-331-71, page 5A-22. Otherwise, check vac m
system components for leaks or malf nctions.
Figure 1—Brake Fluid Sticker Figure 2— aster Cylinder Cover
)

Sec. 5
Page 10
SECTION 5B
A i / i B ' l a k e i
BREATHER AND FILTER
ASSEMBLIES
Figures 1 and 2 illustrate three different
breather and filter assem blies. Figure 1 (left vie )
sho s the original type breather. Replacement is
covered in Service Manual ST -331-71, page 5D-89.
To remove the intermediate type filter (fig. 1,
right vie ) or the latest type (fig. 2), remove t o
scre s and lift cover and filter off housing. To
install, set filter in place on housing and attach
cover. Filters can be cleaned and reused but
breather cannot. If removed, breather must be
replaced ith ne parts.
AIR LINE TORQUE
Refer to page 5B-53 of Service Manual ST-
331-71 and change the follo ing torque values:
3/8-inch from 30-50 to 50-75
}£-inch from 90-115 to 120-150
5/8-inch from 100-125 to 150-200
Also change the statement "retorque to higher
than minimum value" to read: "Retorque to higher
value."
Figure 2—Filter Installed
i

Sec. 6A
Page 11
SECTION 6A
Q a d - a lln e . C n c u n e A ,
The information pertinent to tr ck models covered by this S pple
ment is the same as given in Service Man al ST-331-71 (pages 6A-1
thr 6A-34) with the following exceptions and/or additions:
ENGINE MAINTENANCE
Inspection, adj stment or replacement of em is
sion control related components m st be performed
on a time or mileage basis as indicated. Good
j dgment is req ired in replacement of parts in
those cases where the acc m lated mileage is
s bstantially lower d ring the specified time period.
SERVICING AIR CLEANER
Air cleaners sho ld be inspected and serviced
every 12,000 m iles or more often nder severe
d st conditions; also, whenever dirt is visible in
element or oil. Refer to "AIR CLEANERS” (SEC.
6M) of this s pplement or ST-331-71 Service
Man al.
IMPORTANT: Vehicle operation nder condi
tions s ch as heavy d st, contin o s short trips,
stop and go driving, etc., is not considered normal
se and therefore more freq ent maintenance will
be req ired. S ch additional maintenance req ire
ments are incl ded below where applicable.
Thermostatically Controlled Air Cleaner
The air cleaner sho ld be inspected to make
certain that all hoses and d cts are intact and cor
rectly installed. Operational f nction sho ld be
checked by inspecting position of valve in air intake.
With engine stopped, valve sho ld be open. At
nderhood temperat re below 100°F., with engine
r nning, valve sho ld be partially or f lly closed.
As engine nderhood temperat re rises, the valve
sho ld open.
CHECKING DRIVE BELTS
Fan belt tension on vehicles eq ipped with
V-belts sho ld be adj sted to 120 - 130 po nds on
new belts sing BT-33-73F Belt Tension Ga ge.
Used drive V-belts sho ld be adj sted to 80 - 90
po nds. Ga ge sho ld be placed at center of the
greatest span.
IMPORTANT: After a belt has been in oper
ation one ho r or approximately 50 m iles, it is
considered sed. Belt dressing can be sed to ex
tend belt life. When V-belts are worn they sho ld
be replaced, as excessive tightening will not pre
vent slippage and can ca se damage to bearings.
SPARK PLUGS
Replace spark pl gs at 12,000 mile intervals.
Use of leaded f els res lts in lead deposits on
spark pl gs and can ca se misfiring at m ileages
less than 12,000 miles. Where m isfiring occ rs
prior to 12,000 m iles, spark pl gs in good condition
can often be cleaned, tested and reinstalled in an
engine with acceptable res lts.
ENGINE COMPRESSION
Minim m compression recorded in any one
cylinder sho ld not be less than 70% of highest
cylinder. For example, if the highest press re in
any one cylinder is 150 lbs., the lowest allowable
press re for any other cylinder wo ld be 105 lbs.
(150 x 70% = 105).
This test sho ld be performed to provide rea
sonable ass rance that engine condition is s ffic
iently efficient to prevent leakage of nb rned
gases. If a problem exists, have corrections made.
DISTRIBUTOR POINTS, CAM LUBRICATOR
Distrib tor points sho ld be inspected prior to
performance of t ne- p adj stments. B rned or
pitted points m st be replaced. Points in good con
dition may be re sed after readj stment and the
installation of a new cam l bricator. New points
and cam l bricator sho ld be installed at least
every 24,000 miles.
DISTRIBUTOR CAP
The interior and exterior of the distrib tor
cap sho ld be caref lly inspected and cleaned to
prevent misfiring and deterioration.
SPARK PLUG WIRES
Inspect spark pl g wires for evidence of check
ing or cracking of exterior ins lation and a tight
fit in the distrib tor cap and at the spark pl gs.
Exterior of wires sho ld be cleaned, any evidence
of corrosion on ends removed and wire replaced
if deteriorated.
TIMING, POINTS (DWELL), IDLE SPEED
These adj stments m st be performed acc r
ately, following the specifications shown on the
label nder the hood. Adj stments m st be made
with test eq ipment known to be acc rate.

Sec. 6A
Page 12
GASOLINE ENGINES
Figure 1 — Flywheel ousing and Adaptor Plate
(350 and 366 V8 Engine)
Proper functioning of the carburetor is par
ticularly essential to control of em issions. Correct
mixtures for em ission compliance and idle quality
have been preset. Plastic idle mixture limiters have
been installed on the idle mixture scre s to pre
clude unauthorized adjustment. These idle limiters
are not to be removed unless made necessary by
some major carburetor repair or replacement hich
affects the idle scre adjustment.
POSITIVE CRANKCASE VENTILATION VALVE
Replace the PCV valve at 24 months or 24,000
mile intervals ( hichever occurs first). PCV valve
hose, hen removed for valve replacement, should
be blo n out ith an air hose to make certain that
it is clean. The PCV valve should be replaced at
12 months or 12,000 miles ( hichever occurs first)
hen the vehicle is used under the follo ing con-
ditionsi
• Driving in dusty conditions.
• Extensive idling.
• Short trip operation at freezing temper
atures (engine not thoroughly armed up).
POSITIVE CRANKCASE VENTILATION
SYSTEM - HOSES AND CONNECTIONS
The PCV system should be checked for satis
factory operation at 12-month or 12,000-mile in
tervals using a tester such as the AC Tester CT-3.
POSITIVE CRANKCASE VENTILATION
BREATHER OR FLAME ARRESTER
The breather or flame arrester should be re
moved and cleaned at 12,000 mile intervals. Im
merse in cleaning solvent to remove all deposits
and allo to drain before reinstalling.
MECHANICAL VALVE LIFTERS
Intake and exhaust valves on V6 engines should
be adjusted at 12,000 mile intervals.
MANIFOLD HEAT VALVE
In-Line engines and some V6 and V8 engines
are equipped ith a manifold heat valve hich should
be checked for free operation. A binding valve may
be freed up ith General Motors manifold heat
valve lubricant or equivalent. (NEVER USE ANY
OTHER TYPE LUBRICANT.)
FLYWHEEL HOUSING ADAPTER
PLATE
Figure 1 sho s the fly heel housing adapter
plate used ith 13-inch clutch on 350 and 366 V8
engines.
Inspect engine front and rear mountings as
part of regular engine maintenance program. Be
sure all bracket attaching bolts are kept tight.
Refer to ENGINE MOUNTINGS (SEC. 6D) for engine
mounting information.
UNDERPAN
FLYWHEEL HOUSING
ADAPTER
EXTENSION COVER T-9141

Sec. 6A
Page 13
GASOLINE ENGINES
TUNE-UP CHART
(IN-LINE ENGINE)
Except as otherwise indicated, the following specifications apply to both engine models.
...................................................... .............15-3-6-2-4
ENGINE TY E AND NUMBER OF CYLINDERS .............................. In-Line, 6 -Cyl.
COM RESSION RATIO
250 Engine ................................................................................ 8.5:1
292 Engine................................................................................ 8.0:1
CYLINDER COM RESSION ( SI)
At Cranking Speed........................................................................ 130
Max. Variation Between Cylind ers
...................................................... 20
S ARK LUG MAKE AND NUMBER
250 Engine ..........................................................................A.C.-R46T
292 Engine ..........................................................................A.C.-R44T
Spark lug Gap (A ll).................................................................. 0.035"
lug Tightening Torque (Ft.-Lbs.)............................................. 13-17
IGNITION DISTRIBUTOR
Dwell Angle (D egrees)..................................................................31-34
oint Gap (New)........................................................................0.019”
oint Gap (U sed ) ...................................................................... 0.016”
Contact Lever Spring Tension (O z .)................................................ 19-23
IGNITION TIM IN G .............................. Refer to Ign. System Specs. (Sec. 6 Y)
VALVE LASH..................................................................................Zero
NOTE: Valve lifters are hydraulic type. Refer to “Cylinder Head Bolt
Torque and Rocker Arm Adjustment” in this section for instructions.
ENGINE GOVERNOR SETTING . . . .Refer to Governor Charts at end of Gasoline
Engine Fuel Systems (Sec. 6 M) in this manual.
ENGINE IDLE S EE D ................ Refer to appropriate chart in "Gasoline Engine
Fuel Systems” (Sec. 6 M) in this manual.
FUEL UM RESSURE ( S I)............................................................... 4-5
CYLINDER HEAD BOLT TORQUE (FT.-LBS.) ........................................ 90-100
TORQUE WRENCH SPECIFICATIONS
(IN-LINE ENGINES)
Torque wrench specifications listed below apply to clean dry threads except as otherwise indicated.
ITEM FT.-LBS. ITEM FT.-LBS.
ush Rod Cover B o lt s
...................................................................... 6-8 Main Bearing Cap B o lts ................................................................. 60-70
Cylinder Head B o lts ..................................................................... 90-100 Oil ump B o lts................................................................................9-10
Manifold Clamps (O uter)................................................................ 15-20 Oil Filter (Throw-Away T yp e)................................. (Filter Gasket Oiled 20-25)
Manifold Clamps (Except O uter)...................................................... 25-30 Oil Filter Stud (If U sed )...................................................................45-50
Exhaust-to-lntake Manifold B o lt s ..................................................... 25-30 Crankshaft Damper B o lt ................................................................. 40-60
Thermostat Housing B o lts .............................................................. 25-30 Flywheel Bolts
Water Outlet Housing B o lts ........................................................... 15-20 250 Engines............................................................................. 55-70
Water ump B o lts ........................................................................ 13-17 292 Engines .................................................................. 105 4 1 5
Engine Front Cover B o lts .................................................................. 5-7 Flywheel Housing B o lts................................................................... 25-30
Spark lugs— 5 /8 ” Wrench Size— Tapered Seat lu g ................... 13-17 O il an Bolts
End Bolts..................................................................................8-12
Connecting Rod Bolt Nuts ^ xc- .......................................................................... ®-8
250 En gin es............................................................................. 30-35 Oil an Drain lug B o lts ...........................................................1/2 15-20
292 E ngin es............................................................................. 35-45 7 /8 20-25

Sec. 6A
Page 14
GASOLINE ENGINES
TUNE-UP CHART
(V6 ENGINE)
TYPE AND NUMBER OF CYLINDERS...................................60°, V-6 FIRING ORDER 1-6-5-4-3-2
COMPRESSION RATIO IGNITION TIM ING Refer t Ign. System Specs. (Sec. 6Y)
351C Engines ........................................................7:1 VALVE LASH
CYLINDER COMPRESSION (PSD Intake 0.012”
At Cranking Speed................................................... 125 Exhaust 0.018
Max. Variati n Between Cyl.............................................30 ENGINE GOVERNOR SETTING (N L ad RPM)** If Used
SPARK PLUGS* 351C 3900
Make.................................................................AC IDLE SPEED
............................. Refer t appr priate chart in
Type and Gap "Gas line Engine Fuel Systems" (Sec. 6M) in this manual.
351C..................................................CR 43 N, 0.035”
Tightening T rque (Ft.-Lbs.)..........................................32 FUEL PUMP PRESSURE ................................................ 5-6V2
IGNITION DISTRIBUTOR CYLINDER HEAD BOLT TORQUE (FT.-LBS.) ............................... 60-65
Dwell Angle (Degrees)............................................. .31-34 *|n extremely c ld regi ns use plugs with higher heat range.
P int Gap (New) ..................................................0.019”
P int Gap (Used)..................................................0.016” **With engine br ken in. Full l ad setting is appr ximately 300 RPM
C ntact Lever Spring Tensi n (Oz.) ................................. 19-23 less than N L ad RPM, and will vary fr m engine t engine.
TORQUE WRENCH SPECIFICATIONS
(V6 ENGINE)
T rque wrench specificati ns listed bel w apply t clean dry threads except as therwise indicated.
ITEM
R cker Arm Adjusting Screw
R cker Arm Shaft Bracket B lts
R cker Arm Shaft C ver B lts
Valve Lifter C ver B lts .....
Distribut r Clamp B lt .......
Cylinder Head B lts ..........
Intake Manif ld B lts ........
Exhaust Manif ld B lts ........
Water Outlet Manif ld B lts....
Therm stat H using B lts ....
Fr nt C ver B lts ...........
C nnecting R d N u ts ........
Main Bearing Cap B lts
Main Bearing Cap B lts (Except W Rear) ...................... 130-140*
Rear [Vi" B lts) ............................................... 90-100*
ITEM FT.-LBS.
Oil Pump C ver Screws ............................................. 10-15
Oil Pump t Bl ck B lt . ............................................... 30-35
Oil Filter By-Pass Valve Plug (When U sed)............................. 35-40
Fuel Pump Eccentric B lt........................................... 55-65*
Oil Filter H using t Cylinder Bl ck B lts ........................... 26-36
Oil Filter Center Stud (When Used).................................... 45-50
Oil Filter Assy (Filter Gasket Oiled).................................... 20-25
Spark Plugs .........................................................30-34
Flywheel H using B lts ............................................... 50-60
Flywheel t Crankshaft B lts ...................................... 100-110
Hub-t -Crankshaft B lt (With ut C ne) .............................180-200
Damper r Hub-t -Crankshaft B lt (With C ne) ....................... 240-260
Oil Pan B lts.........................................................10-15
Oil Pan Drain Plug ..................................................20-30
*Oiled with S.A.E. N . 10 Engine Oil. (See Text)
FT.-LBS.
.7-17
20-25
3-5
4-5
12-17
60-65*
25-30
15-20
20-25
20-25
22-27
55-65*

Sec. 6A
Page 15
GASOLINE ENGINES
TUNE-UP CHART
(V8 ENGINE)
Except as otherwise indicated, the following specifications apply to all V -8 oint Opening
engines. New ..................................................................................0.019”
ENGINE M ODELS ........ - ........................................................350,366, 427 Contact Lever Spring Tension (O z .) ............................................... 19-23
NUMBER OF CYLINDERS AND ENG. T Y E .................................. 8 Cyl., V Type p|R|NG 0RD[R 1-84-3-6-5-7-2
COM RESSION RATIO ........................................................................ 8:1
........................... Refer to Ign. System Specs. (Sec. 6 Y)
CYLINDER COM RESSION ( SD
At Cranking Speed........................................................................ 150 VALVE LASH ................................................................................. ero
Max. Variation Between Cylinders ............................................. 20 Note: Valve Lifters are hydraulic type. Refer to “Cylinder Head Bolt
S ARK LUG MAKE S NUMBER ' X i o n s Rocker A™ AdiuStment" ™ thiS f0'
427 .....................................................................................AC-R42T
350 ..................................................................................... AC-R44T ENGINE IDLE S EED .................................. Refer to appropriate chart in
366 ..................................................................................... AC-R43T “Gasoline Engine Fuel Systems” (Sec. 6 M) in this manual.
£ plug liste n in g Torque (Ft. -Lbs .)........... ^13-17 « - UM RESSURE ( SD ........................................................ 7 W
CYLINDER HEAD BOLT TORQUE (FT.-LBS.)
350 Eng....................................................................................60-70
Dwell Angle (Degrees) .............................................................. 28-32 366 & 427 ............................................................................... 75-85
TORQUE WRENCH SPECIFICATIONS
(V8 ENGINE)
ITEM FT.-LBS. ITEM FT.-LBS.
Rocker Arm Cover B o lt....................................................................3-5 Camshaft Sprocket 15-20
Rocker Arm Stud (366 and 427 Only) ............................................ 45-55 Connecting Rod Caps
Distribute, Clamp Boit..............................................................................20-25
W * 'H e a d Bolt c„ , „ Main Bearing Caps (350 Engine)
350 ....................................................................................... 60-70 . D .. 7 n on
366 and 427 Engines............................................................... 75-85 tolfe g! ^ & 4 Only). .V .V .'.'.'.'.V .. . . . V.'.V . .V .V . '.! ! ! !! ! ! :60-70
Crankshaft Damper B o lt............................................................... 80-90 ^ ^ Caps ^ s 4?/ Eng|„es)
Manifold Bolts (Inlet)................................................................... 25-35 |nner ^ 100-110
Manifold Bolts (Exhaust) ^uter B o lts 100110
350 Engine ................................................................ 18-22 Oil ump B o lts 60-70
366 & 427 Engine................................................................... 20-30 Qjl pan
Flywheel Housing and Adapter Bolt (When U sed).............................. 25-35 350 Engines 1/4” B o lts 6-7
5/16” B o lts .............. .’ ............................................................ 12-15
366 and 427 Engines (1/4” B olts)................................................. 4-5
Flywheel Bolts
350 Engine.............................................................................55-65
366 & 427 Engines.................................................................. 60-70 Oil Filter (Filter Gasket Oiled)......................................................... 20-25
Spark lug 5/8” Wrench Size— Tapered S e at........................... 13-17 oil an Drain lu g ....................................................................... 15-20
Water um p............................................................................... 25-35 Flywheel Housing Underpan........................................................ 6-7 1/2

Sec. 6D
Page 16
SECTION 6D
C ' t u j i n e M a u + U i + u j A .
All information in ENGINE MOUNTINGS (SEC. 6D) of Service
Manual ST-331-71, pages 6D-1 through 6D-3 applies to vehicles cov
ered by this supplement ith the follo ing exceptions or additions:
ENGINE CUSHION BOLT AND NUT TORQUE
Bolt to Alum. Bolt to Casting or Nut Nut Torque
Size Torque (Ft.Lbs.) Torque (Ft.-Lbs.) (Ft.-Lbs.)
3/8 ” 16-24 12 - 16 25 - 30 15 - 20
7/16" 14-20 20 - 25 40 - 50 25 - 30
1/2" 13-20 30 - 35 55 - 65 40 - 50
9/16" 12-18 40 - 50 60 - 70 50 - 60
5/8" 11-18 50 - 60 130 - 140 70 - 80
3/4" 10-16 90 - 110 180 - 200 110 - 130 T-9146
MOUNTING BOLTS, BRACKET BOLTS, AND NUT TORQUES
BOLT OR NUT SIZE
1/4" - 20-28 8-10
5/16" - 18-24 20-25
3/8" - 16-24 25-30
7/16" - 14-20 40-50
1/2" - 13-16 55-65
9/16" - 12-18 60-70
5/8" - 11-18 130-140
3/4" - 10-16 180-200
7/8" - 9-14 240-270
1" 8-14 325-380
GM 280-M BOLT
FT.-LBS. e
BOLT HEAD
IDENTIFICATION
GM 300-M BOLT
FT.-LBS.
10-15
25-30
35-45
70-80
85-105
90-110
170-180
300-320
400-430
700-730
BOLT HEAD
IDENTIFICATION
NUT TORQUE
FT.-LBS.
5-8
8-12
15-20
25-30
40-50
50-60
70-80
110-130
210-230
320-350
* 40 - 50
** 55 - 65
*** 60 - 70 Torque for aluminum casting.
ENGINE FRONT MOUNT WITH AT475
TRANSMISSION (ALL ENGINES)
Figure 1 sho s left side front mount used on
In-line 6-cylinder Gas Engine and is typical for V6
and V8 Gas Engines. Refer to page 2 for figure 1.
T-9148
to remove brackets, mounts, spacer, bolts, nuts,
and ashers.
NOTE: It ill be necessary to bend lock tab
before removing the cushion mount bolt (fig. 1) and
after bolt torque. See next page for figure 1.
Replacement
1. Loosen attaching bolts. Raise engine enough 2. Reverse the procedure to install making sure
to torque bolts or nuts as sho n on preceding charts.

Sec. 6D
Page 17
ENGINE MOUNTINGS
WAS ER
•BOLT
NUT
WAS ER
LOCK
‘> " V
FRONT \ V
BOLT
WAS ER NUT
M O UN TIN G
Figure 1—Engine Front ount with AT475
Transmission (Typical)

SECTION 6K
S 't K f i n e G o a U r u j , S y d t e m
Information pertinent to truck models covered by this supplement
is the same as explained in Service Manual ST-331-71 ENGINE COOL
ING SYSTEM (SEC. 6K), pages 6K-1 through 6K-9, except as indicated
by the follo ing information hich is either ne or supplemental in
nature.
Reference should be made to RADIATOR AND SURGE TANK
(SEC. 13) in this supplement for information regarding radiator mount
ing, radiator core and surge tank and cooling system filler cap.
COOLING SYSTEM GENERAL MAINTENANCE
TEST COOLANT LEVEL
Engine coolant should be checked for proper
level regularly (daily if necessary, depending on
severity of service) and every six months for cor
rosion and freeze protection to at least -20 F., or
to the lo est temperature expected during the period
of vehicle operation. Each t o years or 24,000
m iles, hichever first occurs, cooling system must
be drained, flushed, and refilled ith a ne coolant
solution.
RADIATOR CORE EXTERIOR
For proper cooling efficiency, the exterior of
the radiator core and A/C condenser, if so equip
ped, must be kept clean. Light brushing and re
verse air flo is usually a satisfactory cleaning
method. Insects can usually be removed ith a
garden hose using light ater pressure.
COOLING SYSTEM PRESSURE CHECK
Several types of cooling system pressure
checking devices are available locally and manu
facturer's instructions should be follo ed for
proper use. A typical tester is illustrated in figure
1 and procedures are given belo for testing the
pressure cap and cooling system.
1. Testing Radiator Cap
CAUTION: The ra iator cap shoul
not be remove while the engine is at
normal operating temperature. If it is
necessary to remove the cap while the
engine is hot, first relieve the pressure
in the system by turning the ra iator cap
counterclockwise to first stop, using cau
tion not to scal han s. Push own on cap
an turn counterclockwise to remove cap.
a. With radiator filler cap removed, et the
cap gasket ith ater and ash off any sediment
from sealing surface, then install cap on tester.
b. Pump up pressure by operating pump plung
er handle. When the pressure stamped on cap is
reached, observe tester dial and note the rate of
decrease in pressure.
c. The indicator hand on gauge dial should re
main ithin the corresponding pressure segment
of scale for approximately 10 seconds. If pressure
cap does not meet this requirement,it should be
replaced ith ne cap.
2. Testing Cooling System
a. Tighten all radiator andheater hose clamps.
Also, check other connections for leaks at air com
pressor coolant lines, etc.
GAUGE HOSE AND.TAP
PUMP AND GAUGE
ASSEMBLY
FILLER NECK1
SON RADIATOR
OVERFLOW HOSE
Figure 1 — Use of Cooling System Tester (Typical)