Oil only on one side of engine... help?

A small hole on the cam journal must line up with the oil galley that goes to the rocker shaft. Rocker shaft oiling only occurs during a few degrees of crankshaft rotation, and if you spin the crank too fast it is really easy to go past the point of where the oil holes line up.

The bad news is that the cam bearing on the journal that oils that specific side of the motor may not be installed correctly, and the oil galley hole may be blocked.

Do not fire the motor until you can confirm that both rocker shafts are getting oil.