Since you had the pan off, you would have seen some broken parts of a piston or ring in the bottom of the pan.
Or,, some nasty scores/gouges in the cylinder walls from a broken ring.
I doubt if the oil pump would put THAT much of a drag on the motor to where it would be hard to turn over. But,,, anythings possible.
During all this tear-down and reassembly, have you checked the timing gear? Dam near all the 216's had fiber cam gears. It only takes one or two teeth off to mess things up!!
Theres no timing chain on these, just the 2 gears meshing together.
Good Luck,
