First thing. Just because the piston is "up" (TDC mark is up) DOES NOT MEAN that no1 is "ready to fire" IE on the compression stroke.
Every OTHER time TDC mark comes up, no1 fires. The next time TDC comes up, no SIX fires.
When you turn the dist. 1/2 turn this is known as "180 off" or 1/2 turn off.
How do you do this? EASY
There are TWO ways to tell if no1 is ready to fire.
1....A....If either or both valve covers are off, bring the marks up close to TDC. Determine if no1 or no6 valves are BOTH closed. "Wiggle" the crank a few degrees each way to see if either valves move. This is because when you are on the WRONG stroke, both valves are NEARLY equally "somewhat" open........one is closing, the other opening.
If both no1 valves are closed you are on the right stroke. If not, rotate the crank one turn
1....B....The second and probably most popular way is to remove the no1 plug, stick your finger in the hole, and bump the starter until compression just starts to blow your finger out of the plug hole. If you are "new" you might have to go 'round a couple of times
2....Now that you have the no1 piston up AND on the correct (firing, or compression) stroke, it's time to set the dist. Set the timing marks NOT AT TDC, but rather "as they come up" towards TDC stop at "where you want initial timing."
If this is a bone stock 318, etc, set it about 10-12
If you have a bit of a cam, maybe 15
If you have a really wild cam, maybe 20
3...Now with that done, set the dist in with the rotor pointing towards the number one cap tower. Frankly it DOES NOT MATTER where the rotor points as long as you plug the no1 plug wire in where the rotor points.
4.....Rotate the dist. so the vacuum can has room to adjust and is out of the way of the coil bracket, etc.
5.....Rotate the dist towards RETARD (clockwise)
6....Now slowly rotate the dist. ADVANCED ( counter clockwise) until the points just open if you have points, or until the reluctor tip is about centered with the pickup core in the dist.
7....Snug down the bolt
Now imagine the rotor is coming CW. Set the cap on/ off a couple of times to be sure which tower the rotor is APPROACHING. Plug no1 wire in that tower, and wire up the others.
8.....Start the engine. This method, once you learn how, should be close enough that it will fire right up and run, with no more playing.
TIMING LIGHT
You can check timing ON THE STARTER with your light. After you get the above done, hook up your light, "get ready" and crank the engine maybe 5 seconds as you watch the marks with the light. You should be able to clearly see them in dim light. Be sure to "chaulk them up" so you can actually SEE them.
If you have conventional flat tappet lifters, and need to break in a new cam you do NOT want to be cranking on the starter for long periods.
