1.7.1 Gear Train and Timing
DETROIT DIESEL 53
The camshaft and balance shaft gears on an In-line
symbols stamped on the gears. `The letters stamped on
the crankshaft gears identify the proper timing marks
engine
mesh with each other and run at the same
for the particular engine: "I" represents "In-line"
speed as the crankshaft gear. Since the camshaft gears
engine.
"R" represents
must be in time with each other. and the two as a unit
right-hand rotation engine,
in time with the crankshaft gear, timing marks have
and "A" represents advanced timing.
been stamped on the face of the gears to facilitate
correct gear train timing.
Effective with engine serial numbers 3D-64404.
all Series 53 vehicle
engines are built with advanced timing. The timing is
The symbol system of marking the gears makes gear
advanced by aligning the proper "A" timing mark on
train timing a comparatively easy operation. When
the crankshaft gear with the circle-triangle timing
assembling the engine, it is important to remember the
mark on the idler gear.
engine rotation. Then. working from the crankshaft
gear to the idler gear and to the camshaft and/or
balance shaft gear in that order, line up the
appropriate circle symbols on the gears or the
IN-LINE ENGINE:
appropriate triangles as each gear assembly is installed
on the engine. Refer to Fig 1
for a typical
The camshaft and balance shaft gears are positioned
gear train timing arrangement.
so that the circle timing marks are adjacent to each
other (Fig. 1) One circle-triangle timing mark on the
NOTE: It IS advisable to make a sketch
idler gear is aligned with the second "circle" on the
indicating the position of the timing marks
mating camshaft (or balance shaft) gear. The other
BEFORE. removing or replacing any of the
timing mark on the idler gear is aligned with the
gears in the gear train.
proper timing mark on the crankshaft gear.
The crankshaft gear is stamped "IR-A" on the left
The circle and the triangle are the basic timing
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