Piston Rings; Cylinder Blocks - Wisconsin vg4d Repair Manual

LOCATING LUGS
STAMPED
NUMBERS
SHELL
BEARING
Fig. 30
OIL
Fig. 31
lug of both bearing
halves are on the same side as
illustrated in Fig. 30. Refer to chart, Fig. 34, for
clearance between bearing and crank pin.
The piston skirt is cam.ground to an elliptical con-
tour. Clearance between the piston and cylinder must
be measured at the center of the thrust face at the
bottom of the piston skirt. Refer to Chart, Fig. 34, for
proper clearance. The thrust faces on the piston skirt
are 90 ° from the axis of the piston pin hole, with the
wide sect)on of the piston skirt toward the maximum
thrust side, or opposite the crankshaft rotation. ,See
Engine Sectional, Fig. 2. The VG4D was originally
designed with split-skirt pistons which were mounted
with the split toward the direction of crankshaft rota-
tion (clockwise facing flywheel end).
In reassembly; be sure piston and connecting rod as-
semblies are put back into the same bore from which
they were removed. Use a suitable ring compressor
and stagger the piston ring gaps 90 o apart around the
PLACE OPEN END OF
RING ON PISTON
FIRST AS SHOWN
Fig. 32
UPPER END OF PISTON
~
COMPRESSION RINGS
|iii~ SCRAPER RING
OIL RING
Fig. 33
piston. Oil the pistons, rings, wrist pins, rod bearings and
cylinder walls before assembly.
CAUTION: Identical numbers are
stamped
on the side of
the rod with its corresponding cap. These numbers must be
on the same side of the connecting rod when mounted in
engine. Be sure that oilhole in connecting rod cap is facing
toward the oil spray nozzle, as illustrated in Fig. 31. Install
new nuts on connecting rod bolts and torque 28-32 foot
pounds.
PISTON RINGS (Fig's. 32, 33, 34)
If a ring expander tool is not available, install rings
by placing the open end of ring on piston first, as
shown in Fig. 32. Spread ring only far enough to slip
over piston and into correct groove, being careful not
to distort ring. Install bottom ring first and work to-
ward the head of the piston, installing top ring last.
Each piston has two compression rings, a scraper
ring with expander, and an oil control ring. The outer
diameter of the top compression ring is chrome plated.
Mount scraper ring with scraper edge down, otherwise
oil pumping and excessive oil consumption will result.
See Fig. 33 for the correct ring placement.
CYLINDER BLOCKS
Clean all dirt and foreign deposits from between the
cylinder fins and manifold ports.
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