That’s because you don’t set this engine with the distributor like you normally would a TBI engine. The Vortec requires a scanning type OBD2 code reader. You need to set the cam retard angle to 0° +/- 1, I believe, at operating temp with idle set at 1200rpm, if I recall correctly.

 

Cowboytrukr is rite. You need a scan tool that reads cam dwell, or the can position sensor. You do however set the timing with the distributor, but, the truck has to be running at 1100 to 1200 RPMs. You can get the timing close however by setting the #1 cylinder on TDC on the compression stroke, then where #1 spark plug wire is on the cap, you line up the rotor so that it is pointing rite at that spot. The cap needs to be removed for this so you have to mark the distributor, inline with this spot. Rite where #1 is on the cap, there is a corner , or a point. Once you remove the plug wires, and cap, you can see where the prong ia inside of the cap. This is what you want to line up with. Close to where it is in this pic.