How many foot pounds needed to turn mag 5.9?

Since you've got a piston out, pull the rings off it and check the ring gap. See what feeler size gauge you can put in the cylinder and push the piston through with WD40 or other light oil and a moderate push. I'm with Rusty, it's probably rotational. Another question, have high strength rod bolts been installed without resizing the big ends of the rods? Or have the main cap bolts been upgraded without align honing the block?