Need help with ATC 70 compression issues
 

I rebuilt my 82 atc 70 and was running fine, I put the camshaft gear washer on the wrong side, so took it apart to switch it. I have absolutely no compression, if I stick my finger over the spark plug hole nothing. My main qestion is on the valve timing. piston TDC, do you lay the camsaft sprocket with the o mark at 9 oclock or 3 oclock. In turning over my engine by hand it will spark at both locations, need to know proper way to install the camshaft gear and adjust valves, or any other idea of why a fresh rebuild has no compression. Thanks