With the plugs in it'll turn over with a reasonable amount of effort. Don't expect to do it with a 3/8 ratchet, but a 1/2" breaker bar would definitely get the job done. With the plugs out, it's significantly easier, as the engine doesn't have to compress the air. Having the crank bolt loosen or tighten tells me she's locked up tight. Take 10 minutes to remove the valve cover, I'm curious what's under there. Take a good look down the chain guides.
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