Chevrolet 70 1969 Series, Shop Manual

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E N G IN E 6-3
F igure 3 — L o n g itu d in a l B r e a k - A w a y o f V -6 E n g in e
CAMSHAFT AND DRIVE
C am shaft is supported on four bushing type bearings.
All camshaft bearings are pressure-lubricated from engine
oiling system. An oil trough below camshaft holds oil into
which the cam lobes dip as camshaft rotates.
On 401 M and 478M engines the camshaft is gear driv­
en through an idler gear mounted between crankshaft gear
and camshaft gear. All engines have an eccentric which
operates fuel pump. Eccentric is mounted at forward side
of camshaft gear or sprocket.
Timing gears are enclosed by front end cover which
contains a lip-type oil seal assembly. Seal lip seats on pul­
ley hub and prevents oil leakage.
Distributor is driven from gear teeth on camshaft and
oil pu m p is driven from distributor.
The governor spinner valve assembly (standard on
401M and 478M ) is driven from engine oil pump.
Mechanical tachometer (when used) is driven from
socket in rear end of camshaft.
PISTONS AND CON NECTING RODS
Pistons are permanent-mold aluminum castings with
cast-in steel expansion control band. Piston pins are re­
tained by retainer rings installed in grooves in pin bosses.
Piston pins are floating fit. both in the piston bosses and
in the connecting rod bushing.
All pistons have a continuous steel ring groove insert in
which the top ring groove is machined. Pistons are select­
ed to provide proper fit in respective cylinder bores.
Four piston rings are used on both V6 engines. A r­
rangement of piston rings is shown later in this section in
connection with the engine assembling operations.
Connecting rods for all engines are of I-beam type de­
sign. The rod forgings are of heat-treated carbon steel.
CYLINDER HEADS AND VALVE MECHANISM
Two identical cylinder heads of alloy cast iron are used
on each engine. C om bustion chambers are machined to
assure equal volume for all cylinders. Valve guides are in­
tegral with cylinder heads.
W ater passages in cylinder heads serve to quickly carry
heat away from combustion chambers, valve seat and
guide areas, and spark plugs.
Positive type valve rotators and replaceable exhaust
valve seat inserts of special alloy steel are used on both
V6 engines.
Cylinder heads are interchangeable between cylinder
banks.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SH O P M A N U A L