Fig FO83-Distributor basic timing for front mount distributor. (I&T shop manual, FO-4)

Remove necessary wiring for distributor removal (plug wires from distributor cap and high-tension wire from top of coil). Unsnap the coil bail and distributor cap clips, then remove the coil and cap. Remove the two distributor mounting bolts. Remove distributor and take your assembly to the nearest workbench.

Set distributor points to .015 gap. Next, place a straight edge on the wide side of the tang on shaft as shown in fig. FO83. Rotate the shaft until the straight edge is ¼" away from the outside edge of the distributor mounting hole. At this distance, the distributor points should start to open. If not, loosen the timing plate lock screw and turn to advance or retard the timing. Keep adjusting until you get the proper ¼" setting. As you're adjusting, eliminate backlash by turning the shaft backwards and bring the shaft forwards to measure your setting. This ¼" setting will get you static timing at top dead center. That's what you want.

Reassemble in the opposite order. When mounting the distributor back onto engine, the slot in the end of the camshaft (front of motor) is offset. So the tang on the distributor can only mate easily to the slot on the engine camshaft one way. It will slide on easily without force and fit flush to the motor. If the tang is 180 degrees off, the distributor will have to be forced on and as soon as you tighten down the mounting bolts, the casting on the distributor will break. It may be in your best interest to mark the position of the tang with a couple of marks on the back of the distributor upon removal from the engine.