Gear Train and Timing
DETROIT DIESEL 53
Fig. 1. - 6V Engine Gear Train Timing Marks (Standard Timing Shown)
symbols stamped on the gears. The letters stamped on
The two camshaft gears mesh with each other and run
the crankshaft gears identify the proper timing marks for
at the same speed as the crankshaft gear. Since the
the particular engine:
camshaft gears must be in time with each other, and the
"V" represents V-type engine, "R" represents right-hand
two as a unit in time with the crankshaft gear, timing
rotation engine, and "A" represents advanced timing.
marks have been stamped on the face of the gears to
facilitate correct gear train timing.
The symbol system of marking the gears makes gear
train timing a comparatively easy operation. When
assembling the engine, it is important to remember the
The timing is advanced
engine rotation. Then, working from the crankshaft gear
by aligning the proper "A" timing mark on the crankshaft
to the idler gear and to the camshaft balance shaft
gear with the circle-triangle timing mark on the idler
gear in that order, line up the appropriate circle
symbols on the gears or the appropriate triangles as
each gear assembly is installed on the engine. Refer to
Fig. 1 for a typical gear train timing arrangement.
NOTE: It is advisable to make a sketch
indicating the position of the timing marks
BEFORE removing or replacing any of the
gears in the gear train.
The circle and the triangle are the basic timing
1972 General Motors Corp.