help with my 93 240sx

I had to replace the head, camshafts, and lower timing chain guides on my 93 240sx hatchback. I bought head off of one friend and camshafts off another friend. All camshaft shims placed and adjusted. I have cylinder #1 on TDC, all mating marks are lined up for the crank, idler sprocket and camshaft sprockets. Put everything else back together. Tried to start her and she wouldnt even cough. Checked set up with distributor, is set to #1 firing position on TDC. Check spark to plugs and they all fire. Ran a compression test and only getting 90 PSI in each cylinder. FSM calls for 150-180 @ 300 RPM, don't know if the starter is turning over that fast. I checked valve seats before I put it on and didn't notice anything out of the ordinary. Even if some of the valves weren't seating, I should get a different reading for PSI in each cylinder , I would think????? Can anyone help me out, Thanks