crank bolt, loose? Options

[doobie123]

working on my porsche 914, 2.0, 5 spd
i'll try to keep this short and still give the details so...
i had the drive train out to do the clutch/flywheel and decided to freshen the top end. the car ran fine when i got it but, the clutch was bad so i took the plunge,(something i never did before) and went for it.
put it back together and test drove it. it ran fine for the first mile or so but on my way back to the shop, it started making a banging or, knocking noise. i decided to check the valves and use the method of pulling the plugs and turning the cage by hand. pulled the plugs, went to turn the cage and it was loose. i was able to rock it and when i turned it, the cage turned but not the three bolts holding it. upon further inspection, i was able to turn the center bolt, (crank bolt?) with my fingers.
i got a socket, (13mm) on it and can tighten it down but before it tightened, i could feel a clicking through the wrench.
so my questions are does it just tighten on the cage? should there be a key way that the cage needs to engage? will tightening it the torque specks do the trick or do i need to drop the engine again? is there a chance i've done damage by running it?
i know that there is a unknown as far as the damage but i'm just looking for some suggestions as to where i go from here.
thanks