STOP!!!!!!!!!!!!!!! you need to pull the head off the engine and inspect, or shove a boroscope in the plug hole and have a look. you'll probably find that a lot of carbon buildup on the inside of the head has caused the compression ratio to go up, thus making it hard to crank. the other thing you might find is debris, or corosion in the bore. either of those need to be removed before you try to run the engine, or you could do a lot of dammage. a head gasket is really cheap compared to a rebuild. if the problem is just from carbon, take a wire brush in a drill and clean the head before reinstaling.
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