I'd like to throw in a little experience here just to avoid confusion for the reader who may be reading this thread and thinking that distributor orientation has anything to do with ignition timing.
Distributor orientation does not affect ignition timing.
From both the service manual and experience with the 24x signal from a distributor (prototyping only), the PCM is monitoring the 24x crank signal to determine crankshaft position. However, this is not enough for the PCM to know when to fire the injectors/coils. The PCM uses the 1x cam signal to determine engine stroke (intake or exhaust). If no cam signal is present or the cam signal is not in proper orientation, the PCM will attempt to start the engine as long as it sees the 24x crank signal (engine rotation is present). If the engine does not start (no increase in RPMs), the PCM will assume opposite stroke in an attempt to start the engine (extended cranking and typically backfire).
So don't get too caught up on the distributor orientation. Follow the instructions provided (as per GM) and expect reliable starts 100% of the time.
There's nothing wrong with knowing for sure that the cam sensor orientation is 100% accurate...but GM does not reveal this information. Probably because it's not critical.
Of the several vehicles already up and running with 24x, no one has had startup issues or DTCs indicating improper camshaft orientation.
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