Very low compression

[challenger]

Working on a 1998 Altima with over 200,000 miles. Car just died and won't re-start. I've got fuel, spark and will crank over. Don't have anything leaking, no water in oil. Did a compression test and had very low compression on all cylinders nothing above 50-55 psi. Pulled the valve cover couldn't see anything visually out. Rotated number one cylinder up to TDC, rotor pointing to number one plug and the first cam lobes next to the chain side pointing out. (The cam chain and sprocket marks DON'T line up!!!) I found the crank chain extremly loose and the large straight chain guide gone. I pulled the lower oil pan and found bits and peices of the guide. My question is would the chain skip that much to cause the head (valves) to allow for the low compression. If it were rings I think the readings would be up and down, not all about the same. I know everyone here says these chains are pretty strong, but could this be my problem? Any help on "how to" would be great. I'm not finding much about these motors so I'm having to piece it together. I found another post about having to rotate the crank around multiple times to bring all three marks for the cam together. I did that last night and today I'll pull the lower crank cover off and check that part. The right large guide is gone and i'm still not sure if thats enough to cause the low pressure across all four cylinders?? Still looking for the smoking gun!
Modified by challenger at 5:37 AM 2/3/2010