RE: How to time a 97 blazer 4.3 vortec
1 Align the indent hole on the driven gear with the paint mark on the distributor housing
Ensure that the distributor rotor segment points to the cap hold area
2 Align the slotted tang in the oil pump driveshaft with the distributor driveshaft. Rotate the oil pump driveshaft with a screwdriver if necessary
3 Install the distributor and distributor clamp. The flat in the distributor housing must point toward the front of the engine.
4 Once the distributor is fully seated, align the distributor rotor segment with the number 6 pointer (1) that is cast into the distributor base. If the distributor rotor segment does not come within a few degrees of the number 6 pointer (1), the gear mesh between the distributor and camshaft may be off a tooth or more. Repeat the procedure again in order to achieve proper alignment
The flat in the distributor housing must point toward the front of the engine