SERVICE MANUAL
CONNECTING RODS, PISTONS, RINGS & SLEEVES
Section 5
The cutback land design uses combustion gas pressure
to push the top compression ring down against the top
piston ring grooves and out against the cylinder sleeve.
Because the top ring is held tightly against the piston and
cylinder sleeve, only a small amount of lubricating oil
enters the combustion chamber and is consumed.
Balance Pressure Piston
DT-414, 436 and 466 w/ S/N 38089 and up, and DT-
414B, 436B, 466B and 466C engines w S/N 76440 up,
have Balance Pressure pistons. These pistons have the
cutback land design and a wide groove below the top
ring (Fig. 4). The intermediate piston ring used with the
Balance Pressure Piston has an increased end gap of
approximately .070 inches.
During engine operation, combustion gases that pass the
top piston ring enter the wide groove. They move past
the wide gap intermediate ring into the crankcase area
and subsequently are discharged to the atmosphere
through the new valve cover mounted breather. The top
piston ring always has higher combustion pressure
above and lower pressure below because gases passing
the top ring are vented past the intermediate ring end
gap and to the atmosphere. The Balance Pressure
Piston design provides outstanding oil control.
Figure 3. - Cutback Land Piston
(Turbocharged only)
Following is a list of acceptable combinations of
ventilation system, piston rings and pistons:
Figure 4. - Balance-Pressure Piston
NOTE: The technology utilized in designing the new
piston and ring combination represents a significant
advancement in engine oil control.
The oil-regulating ring provides an even distribution of
lubricating oil which aids in friction reduction and cooling
action for the piston and cylinder sleeve. Excess oil is
wiped by the rings back down to the crankcase.
The PISTON PIN is induction-hardened steel and
anchors the piston to the connecting rod. The pin is
retained in the piston by retainer rings in its bushing in
the upper end of the rod. The aluminum alloy of the
piston is excellent bearing material and no bushing is
required between the pin and the piston.
CGES-185-3
PRINTED IN UNITED STATES OF AMERICA
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