TM 5-3895-346-14
CYLINDER BLOCK
ENGINE OVERHAUL
The main bearing bores are line-bored with the bearing
caps in place to ensure longitudinal alignment. Drilled
passages in the block carry the lubricating oil to all moving
parts of the engine, eliminating the need for external
piping.
The top surface of the in-line block is grooved to
accommodate a block-to-head oil seal ring. Also, each
water or oil hole is counterbored to provide for individual
seal rings (Fig. 3).
Each cylinder liner is retained in the block by a flange at its
upper end, which seats in the counterbore in the block
bore. An individual compression gasket is used at each
cylinder. When the cylinder head is installed, the gaskets
and seal rings compress sufficiently to form a tight metal-
to-metal contact between the head and the block. The in-
line cylinder blocks were revised at the idler gear hub
mounting pads, to increase the rigidity of the flywheel Figure 2. Air and Water Passages in In-Line
Cylinder Block
housing, by increasing two of the three 5/16-18 boltholes of
each mounting pad to 3/8-16 boltholes (Fig. 4). The 3/8-16 boltholes were incorporated in engines beginning
with serial number 4D-103. Revised end plates, end plate-to-block gaskets, and flywheel housing are required
with the change in bolt sizes. Only the revised cylinder blocks are available for service.
The in-line cylinder blocks have also been revised to improve the breathing characteristics and increase the
flow of the lubricating oil returning from the cylinder head to the engine oil sump by the addition of two vertical
oil passages directly under the camshaft and balance shaft at the front end of the cylinder block (Fig. 5).
Cylinder blocks with the vertical oil passages were used in engines beginning
Figure 4. Location of the Four 3/8-16
Figure 3. Cylinder Head Gaskets and Seals
Boltholes in Rear of Cylinder Block
in Place on Cylinder Block
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