273 timing sprockets help

Im in the middle of tearing apart my 273 for a cam and lifter and timing chain replacement when I ran into a problem. I can't seem to get the timing chain and sprockets off. The cam sprocket wants to come off only to a point then, when I try to get the crank sprocket loose it does not budge at all. Is there some trick or method to getting them off. This is my first time replacing a cam. The books I read say both must come off together and it is a back and forth affair between crank and cam. However, my crank sprocket "feels" welded on its so tight. What is the secret I can post pics if that helps at all. Thanks