Ign. timing (was dist. indexing, too much cam)

What should the base ign. timing be at idle?

In my search for some of the odd symptoms I'm getting after the rebuild I checked the timing this morning at idle and it is sitting at about 12*. The odd thing is at idle it seems to bounce around quite a bit. It will jump up to 16 -18 and back down to 8-10 and then settle in at 12 for a couple seconds then do it again. When it jumps it is a very quick sporadic kind of thing taking not even a second to jump up, down, and back to twelve again. With the wife bumping the RPM up to 900-1000 it stays a nice steady 12 -14*. As more throttle is added it advances like I think it should.

Still trying to understand the system so I've got a couple more questions as well. Will turning the dist. housing small amounts affect the timing I see with a light (ear is ground off for indexing)
or does it only affect the relationship between the cam sensor and the CPS?

I also went through and checked the vacuum system again and there are no leaking lines. Found the check valve ( located at the manifold on my '93) and pulled it after the jeep had sat all night. Still a good strong vacuum left in the bottle and lines.

Found another odd thing that leads me to believe I may have a head gasket prob. but I will put that in another post.

Thanks

Tim

If the timing "flickers" back and forth sort of jerky and extremely rapid...sounds mechanical...very loose timing chain or sloppy distributor internals...possibly a missing camshaft thrust pin or broken spring...is the engine noisy?? But i guess it could be in the engine control/ignition system too...