Buick LeSabre 1965 Service Manual page 34

2 - 1 2 ENGINE DESCRIPTION
ENGINE
Figure 2-4—401 Cubic Inch Engine End Sectional View
The crankshaft is counterbalanced
by weights forged integral with
crank cheeks. Maximum counter-
weighting in the space available
is obtained by machining the
weights to a contour which allows
a minimum uniform clearance
with cylinder barrels and piston
skirts. Additional counterbalanc-
ing is obtained by an offset fly-
wheel flange.
All engines are equipped with a
harmonic balancer and fan pulley
assembly.
c. Connecting Rods and Pistons
Connecting rods are steel forg-
ings of I-beam section, having
bosses on each side so that metal
can be removed as required to
secure correct weight and balance
during manufacture. The lower
end of each rod is fitted with a
steel-backed full precision type
bearing. The upper end of the
connecting rod has a hole into
which the wrist pin is pressed.
The outer ends of the pin float
in the bosses in the piston.
The tin plated aluminum alloy
pistons have full skirts and are
cam ground. Two compression
rings and one oil control ring are
located above the piston pin. Two
transverse slots in the oil ring
groove extend through the piston
wall and permit drain back of oil
collected by the oil ring. Shallow
depressions cast into the head
provide clearance between the
piston and valves in operation.
See Figure 2-4.
The cast iron compression rings