Disassembly begins with breaker...
Disassembly begins with breaker point and condenser removal. Next, disconnect and remove the vacuum advance unit. Don't lose the tiny C-clip, which is easy to misplace.
Once you have the initial timing dialed in at around 6-12 degrees BTDC at idle, you're ready to work on total timing and how quickly it arrives. Aim a timing light at the balancer and watch what happens to timing as you increase engine speed. Total timing, around 34-36 degrees BTDC, should be in by 3,000-3,500 rpm. Avoid going beyond 36 degrees BTDC. Depending on how your engine is configured, 34-36 degrees BTDC should be optimum. This means holding the throttle at 3,500 rpm and watching total timing with the vacuum advance connected. Total timing should be in by 3,500 rpm. The trick is adjusting both vacuum advance and mechanical advance so timing follows rpm as you open the throttle. When you goose the throttle and rev the engine quickly to 3,500 rpm, timing should follow the rpm without pre-ignition (pinging or spark knock). If there is spark knock as you jab the throttle or under hard acceleration, you have too much timing (timing too far advanced). If your engine falls on its face, you don't have enough timing.
There are some who will insist that you can take total ignition timing to 38-42 degrees BTDC. But do you want to risk your engine? Excessive timing may make more power, but you run the risk of engine damage because spark knock can melt pistons and break ring lands. Forty years ago, you might have been able to get away with 38-42 degrees BTDC total timing with 100-octane gasoline. Today, it's risky business with 87-92-octane pump gas.
Once you have mechanical advance timing dialed in, vacuum advance adjustment is easy. Aftermarket vacuum advance units adjust with an Allen wrench via the vacuum port. Watch the rate of advance when you goose the throttle to 3,500 rpm. How quickly does the timing mark move? If it moves quickly to total timing before the engine arrives at 3,500 rpm, you need to slow down the advance rate by turning the Allen wrench clockwise. This places more tension on the advance spring, which slows advance rate. Counterclockwise reduces tension, which in turn speeds up the advance rate.
If you're using a Ford vacuum advance unit, it works the same way with a different approach. Add shims to the advance spring if you want to slow down the advance rate. Eliminate or reduce the number of shims if you want to speed up the advance rate. When mechanical advance and vacuum advance work together, as they should, you get total timing, which is the most important timing element of all.
 |  This is an aftermarket vacuum...  This is an aftermarket vacuum advance unit, which is probably what you will find during distributor teardown. Aftermarket vacuum advance units are adjustable with an Allen wrench via the vacuum port. |  With the breaker plate removed,...  With the breaker plate removed, you can see the centrifugal (mechanical) advance, which is a pair of spring-loaded flyweights that advance spark timing as rpm increases. Flyweights move outward with rpm, advancing the rotor and spark. Spring tension, which is adjusted by bending the advance adjustment arms, controls exactly when advance begins to roll in to make the spark earlier. The "10" indicates half the total number of degrees this rotor will advance, meaning 20 actual degrees. |
 The toughest task is removing...  The toughest task is removing the distributor cam, which is retained by a wire C-clip. This is also where the felt lubrication wick goes. |  You don't have to do this,...  You don't have to do this, by the way, because the distributor shaft will come out regardless. We wanted to take this distributor completely apart to show you where everything goes. |  The distributor drive gear...  The distributor drive gear and shaft retainer collar are secured with tension pins. Drive both pins out with a punch. Mark both retainer and gear to the shaft because they must go back on exactly the same way to keep dimensions constant. |
 Use an oil pump shaft to drive...  Use an oil pump shaft to drive the distributor shaft out. Be extremely careful because the assembly can cock under hydraulic pressure, causing injury. Gently drive the shaft out in baby steps. The toughest step is getting it loose. Once the shaft breaks free, it's a smooth trip out. |  You can clean up the shaft...  You can clean up the shaft before using the hydraulic press to ease removal. The barber pole grooves carry engine oil to the bushings and shaft. | |