GMC 1990 Light Truck Repair Manual page 461

NOTICE: The inertia weight section of the
torsional damper is assembled to the hub with
rubber type material. The correct installation
procedures (with the proper tool) must be
followed or movement of the inertia weight
section of the hub will destroy the tuning of the
torsional damper.
2. Stud (item A, figure 32) to the crankshaft. Thread
the stud fully into the tapped hole in the crankshaft.
Figure 30—Installing the Camshaft
Figure 29—Camshaft and Components
A. Align Marks as Shown
B-07892
4.3 LITER V-6 6A3-19
Figure 31—Timing Marks
A. Installation Stud
B. Nut
C. Washer and Bearing
Figure 32—Installing the Torsional Damper
B-05289
B-07880