How difficult should it be to turn over by hand??

I finally had the chance to put my 273 complete rebuild together over the last week and went through the steps in a mopar book as far as assembling pisotns, rods, bearings. I had the rods and crank turned 10/10 and it seamed fine when i installed the crank, turned pretty easy by hand without any wrenches (is that normal?) I gaped the rings to specs and now that its completely assembled without the heads on its really hard to turn over with a huge crescent wrench, but once it gets started its a bit easier to move. I noticed after leaving it alone for an hr that when i came back to turn it i nearly tipped to engine off the stand to get it to turn, is this normal?


Thanks,

Jake