Timing and Distributors

I am having a bit of trouble getting my car to run smoothly. 76TR) The bible
says 4 deg at idle.
Is this realistic and if it is then I will have to pull the Distributor and
rotate it . The best I can get is 10 Deg at idle and that is with the
Distributor turned all the way into the motor.
What am I missing  ?
The car smooths out as the timing gets closer to 10 but is not quite there.
Thanks for any help.

Crabby