timing problem

I'd do the protractor thing or put the timing light on it and keep increasing RPM until the advance stops and note the amount of advance and RPM. Then do a little math to find mechanical in the distributor. You might have to limit the mechanical.

Make sure you set timing with vacuum adv disconnected and the port at carb plugged.

There's usually an allen/hex key adjuster in the vacuum canister to adjust amount of vac adv available. A little trick is get your initial set, then hook the vacuum adv hose to a direct vacuum source, note the change in timing. That's the amount of vacuum advance in the canister. Twist the adjuster either direction to get the amount of adv you want coming in from vacuum.

Dave and Juvat have you headed the right direction.