You should bear in mind that the most common cause of your symptom is an intake manifold leak or a very minor carburetor problem. You have disturbed both of those areas recently, which brings them close to the front of the list. My valve comments were based on the idea that you had not dismantled anything, and had just freed up the stuck valve by bumping the rocker arm. If the tappet clearances are correct, any sticking valve problem would fix itself with a couple of minutes running, and there is even a chance that a valve seating problem would also fix itself, so long as you were running it without load. You haven't left a vacuum hose off have you?
