Simply put and without a doubt, your car should never and I mean never run 16.50s. Falling out of a tree it would run faster than that. Your problem lies in the timing and/or the carburators. Degreeing in your camshaft will not turn your car from 16.50 to high 14, or 13 or 12. Lining up the marks should be ok. You spend your time having someone work on the above and you will get into the low 14s I would think minimum. If you were having fuel delivery problems with the fuel pump you would probably feel it fall off and the front end dip because of fuel starvation. Remember, carbs (including vacuum issues) and distributor.