Do you have the cylinder head off the engine? How are you turning the engine? Does it seem to turn easily enough with the starter? If the engine is fully assembled and you are turning it by pushing on the fan belt and turning the fan, it should turn easily, but may give the impression of being 'stiff.' If the engine has been rebuilt and not run, the engine will be stiff because of ring tension and/or tight bearings. The rear seal on the crankshaft will make a newly rebuilt engine very hard to turn when the rear main bearing is properly fitted and tightened. If the engine has been standing for quite a while, as indicated by the stuck lifters, the cylinder walls and bearings may be dry and will cause the engine to be somewhat hard to turn.
If the engine hasn't been run for a long time, I would first remove the distributor and drive the oil pump with a screwdriver bit inserted into an electric drill. Keep driving the pump for a minute or so after you get oil pressure, to make sure oil has been delivered throughout the engine. Put the distributor back in the engine, then squirt an ounce or two of oil into each cylinder (3-4 squirts from a pump oil can), then turn the engine a few turns however you can. If that doesn't help, and the engine still resists turning, it might be disassembly time. Or you can start it, if it will, and see what happens, although I would go cautiously with that idea. But if you hear any clanking or clunking while you crank the engine, don't start it- its disassembly time.
Harvester
