Originally Posted by dabnis
Not even close to being an expert on anything but do have some years working on gas and diesel engines. The crank being hard to turn when only the #1 valve train operates is interesting, perhaps an out of tolerance camshaft, bent valve stem, seized valve guide, galled cam lobe or rocker arm? For starters a compression test on all cylinders should be done.
When things settle down when operating the de- compression lever on #1 leads me to think of the above valve issue(s) or perhaps a blown head gasket in the #1 area. Let us know what you find.
A compression test has been suggested a couple of times. Don't know if one was done, but it sounds like the head has already been taken off. If #1 piston doesn't come all the way up it is likely to be a bent rod.