TM 5-3895-346-14
ENGINE OVERHAUL
CONNECTING ROD
CONNECTING ROD
Each connecting rod (Fig. 1 and 2) is forged to an I-section with a closed hub at the upper end and a bearing
cap at the lower end. The connecting rod is drilled to provide lubrication to the piston pin at the upper end and
is equipped with a nozzle to spray cooling oil to the underside of the piston head on engines equipped with an
oil cooler. Engines that are not equipped with an oil cooler do not use nozzle-type connecting rods. An orifice is
pressed into a counterbore at the lower end of the oil passage (in rods equipped with a spray nozzle) to meter
the flow of oil.
CAUTION
Never intermix nozzle-type connecting rods in an engine with non-nozzle-type
connecting rods.
A helically-grooved bushing is pressed into each side of the connecting rod at the upper end. The cavity
between the inner ends of these bushings registers with the drilled oil passage in the connecting rod and forms
a duct around the piston pin. Oil entering this
Figure 1. Connecting Rod Mounting
cavity lubricates the piston pin bushings and is then forced
out the spray nozzle to cool the piston. The piston pin
floats in the bushings of both the piston and the connecting
rod.
The turbocharged engine connecting rods include vapor-
blasted bushings and increased width oil grooves.
F
i
Figure 2. Connecting Rod Details and
Relative Location of Parts
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