The distributor turns with the cam, which is half the RPM of the crank. So you not only need to be at TDC for #1 (or whatever cylinder you want to point the rotor at), but you also need to be on the compression stroke for that cylinder. To do that, remove that spark plug and place your thumb over the hole. (or you can install the compression gauge) Tap the engine over with the starter a little at a time until you feel the pressure push past your thumb (or see the compression rise), then rotate it slightly further until you are at (or slightly before) TDC. Then point the rotor just before that cylinder wire when you put the distributor in. If you want to get it even closer you can hook a timing light up and rotate the ditributor with the engine sitting before TDC until it sparks.